When comparing Simplenote vs Dropbox, the Slant community recommends Simplenote for most people. In the question“What is the best cross-platform note-taking app?” Simplenote is ranked 4th while Dropbox is ranked 38th. The most important reason people chose Simplenote is:
Simplenote takes a minimalist approach to its interface. There are no toolbars full of formatting options or extra features like notebooks to group notes. The entire desktop interface consists solely of a sidebar with your tags and trash filters, the list of existing notes with search, a button to add a new note and a simple view for looking an existing note or writing a new one.
Specs
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Pros
Pro Very simple and clean interface
Simplenote takes a minimalist approach to its interface. There are no toolbars full of formatting options or extra features like notebooks to group notes. The entire desktop interface consists solely of a sidebar with your tags and trash filters, the list of existing notes with search, a button to add a new note and a simple view for looking an existing note or writing a new one.
Pro Geared towards fast usage
Unlike alternatives (such as Evernote) that are laden with features, Simplenote is fast to use and sync. Reviews from the Verge, Lifehacker, and a variety of other sources all describe using the Simplenote apps as very fast. While it may not be as feature-rich as other apps, the responsiveness of the app and simple interface keep it easy to use while never slowing down the user when they need to quickly take a note.
Pro Works offline
Users can edit and create documents offline, can then sync their content the next time they are online. This way a user can work even when there's no data connection without the worry of losing work.
Pro Desktop app is open source
The desktop version of Simplenote is hosted on the GitHub and since it is open source, it can allow developers to fork the code in order to improve the app.
Pro Can export your data
The program enables exporting of notes as text documents.
Pro Collaborative features
Notes can be shared with others or worked on collaboratively.
Pro Open Source
All of the Simplenote apps are open source and ready for your contributions! You can find the source on GitHub:
iOS: https://github.com/automattic/simplenote-ios
Android: https://github.com/automattic/simplenote-android
macOS: https://github.com/automattic/simplenote-macos
Electron (Windows and Linux): https://github.com/automattic/simplenote-electron
Pro "Time machine" style revision control on the notes
Each edit of a note is saved in order to allow the user to go back to a previous version of a document. This way, if mistakes are made or something is deleted, you can go back to the previous version without any hassle.
Pro Wide range of great clients with great sync
Official native apps are available on popular platforms such as Android, iPhone, iPad, Kindle, OS X, Windows and Linux. Open-source clients extend this support even more widely to various other platforms, such as webOS and the BlackBerry PlayBook. These apps embody the core philosophy of Simplenote: minimalism and focus on the note taking.
There are multiple unofficial clients (including the excellent Notational Velocity and NValt, a fork of the app with markdown support and other goodies.)
Pro Markdown support via web interface
There is support for Markdown when using the web app. This can be convenient for those who want to use Markdown in a particular note.
Pro Linux client available
Pro Excellent iOS app
Pro Excellent desktop client in the form of nvAlt
Pro Easy to use
You can use Dropbox via website, by installing a desktop client that creates a folder that you simply drag and drop files into, or with their mobile app. Everything synchronizes across all devices used and cloud storage. And Dropbox offers easy methods of sharing whatever is within it.
Pro Cross-platform desktop and mobile
Dropbox is available on iOS, Android, BlackBerry, Windows, OS X and Linux. By having a client for so many OS's pretty much anyone is covered no matter what kind of device or OS they are using.
Pro Allows sharing a folder
Using a desktop client: right click on the folder you want to share and select Dropbox > Share This Folder, then enter the e-mail addressees of people you want to share the folder with.
Pro Smart updates to big files
If a small portion of the file is changed it sends/receives only the differences (not the whole file), which is fast and bandwidth-efficient.
Pro Allows sharing a single file via link
Whether using desktop client or web interface, simply right click on the file you want to share and select Dropbox > Share link, then send the link to the people you want to share the file with. The recipient does not require a Dropbox account.
Pro Up to 18GB of free storage space
Dropbox personal accounts start out free, with 2GB of space, but users can get extra space by recommending the site to friends, or taking part in events like "Dropquest", where users can win extra space by solving puzzles.

Pro Linux support
Dropbox offers native Linux support, integrates with Nautilus file manager.
Pro Reliable
Pro Desktop client has no file size limit
As long as you have enough storage available, you can upload files of any size using Dropbox desktop client.
Pro Folders can be downloaded compressed to save bandwidth
To save bandwidth and download speed you can choose to compress a folder into a zip archive for download.
Pro Adjustable bandwidth use
To not slow down the network or save traffic you can limit the upload and download speeds of Dropbox.
Pro Lots of addons and integrations
There are official and third-party Dropbox add-ons that extend the functionality of the service and add ease of use of existing features.
Additionally, Dropbox can be integrated with existing applications to bring its functionality to other apps.
Pro 30-day version control
Dropbox keeps deleted and earlier versions of files for a month.
Pro Instant disaster recovery
Your files always synced online means instant disaster recovery. When your hard drive becomes unbootable, pick up another laptop and just carry on with your life from where you last saved.
Pro Available free storage can be increased with referrals
You get extra free space for you and your friend if they sign up.
Pro Fast sync speed
Cons
Con No note encryption at rest
Notes are encrypted in transit, but remain unencrypted on Simplenote's servers.
Con Limited ways to reorder notes
You are able to sort your notes alphabetically, date modified, or by last created. There is no way to drag and drop the notes to create a custom order.
Con No reminders
You cannot set reminders to revisit a specific note or complete a task.
Con No support for file attachments
Simplenote doesn't provide support for embedded attachments. This can limit the use for some as many other note-taking apps do support this type of feature.
Con Search is limited to one tag
There seems to be no way to find notes that have both tag X and tag Y. This isn't a big deal until you have a large library of notes, and want to cross-search for two things at the same time to vastly narrow down your search.
Con No way to import notes from anywhere
Con Web access only for updated browsers
They recently removed support for older browsers, and it's not working on the latest version of Waterfox. You need an updated version of a well-known browser.
Con No 32-bit version
Con The search function doesn't see tags
If you search for 'foo' you won't find notes with tag foo. In that regard, tags are completely isolated from the search.
Con No way to bulk-apply a tag
This is a typical workflow action in other apps: Do a search, multi-select notes among the matches, then apply or de-apply one or more tags to all these notes at once.
There's no way to do this in Simplenote. The only bulk operations are Delete and Pin-to-top.
Con No notification when changes made on a shared note
Currently, there is no way to be alerted when a change is made by another contributor on a shared note.
Con Save-to-disk feature is poor
The only way to download your data off Simplenote is via a "download zip" feature that unfortunately loses all the semantic structure of your data (tags, for instance).
Con No integrated social media sharing
The only way you can share notes with others is with a link you're given when you publish your note. There is no integrated social media sharing if you directly want to post your note to Twitter, Facebook, etc.
Con Lack of color impacts usability
There are two themes available, the default theme and a dark theme.
Both use only the single solid color (either white or black) for the background, so there is a lack of visual cues to separate what you're looking at.
Con Too little free space
There is just too little of free space available comparing to the competition.

Con Not secure
They don't apply end-to-end encryption, files are visible to admins, governments, etc..
Con No privacy
Extensive collecting and distribution of user data to commercial third parties.
Con Consumes a lot of CPU resources when syncing many files
Con All-or-nothing (non-selective) upload
Uploading generated contents (cache, compiled code, etc.) is prone to conflicts, wastes bandwidth and free space.
Con Low bandwidth
Con Dropbox keeps deleting features, chasing customers away
For instance, all photo albums got deleted. It used to be very easy to share a couple og photos, now it's PAINFUL and must be done file by file.
Con Nocive development model
Takes a lot of decisions that usually damage community, from deleting features to making impossible to use with other filesystems than ext4 because they decided without a plausible reason (they said it was about xattrs, but all modern linux filesystems supports xattrs, so it's bs.)(they remove this later, but it's too late).
Con Problems when synching between Linux and Windows devices (unconfirmed)
This summer I lost thousands of files due to this problem on older projects which subsequently needed revising and had to be rebuilt as tons of the source was gone.
Con Restricted only to 3 devices for FREE accounts
Recently dropbox decreased the number of linked devices to 3, so you can't have more than 3 linked devices. This is problematic if you use Dropbox to sync between your computers.
Con Can unintentionally delete your files if you reinstall your OS without closing Dropbox
If you reinstall the operation system for your PC and you do not close Dropbox, it will delete all files.
