When comparing Photoshop vs Pixly, the Slant community recommends Pixly for most people. In the question“What are the best pixel art / sprite editors?” Pixly is ranked 14th while Photoshop is ranked 16th. The most important reason people chose Pixly is:
RGB, CMY, HSB, and a somewhat different HUSL.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Industry standard
Photoshop is used by professionals everywhere in a wide variety of fields including photography, graphic design and digital art. It is the de facto standard for image manipulation. If you've seen a magazine ad featuring a model, you've probably seen the effects of Photoshop. You won't be alone when using Photoshop.
Pro Trove of plugins that extend functionality are available
A wide variety of plugins that add new effects, improve existing functionality and simplify workflow are available.
Pro Lots of tutorials
There's a huge number of both free and paid tutorials available online. Websites like Lynda.com offer premium high-quality, in-depth tutorials, but there are plenty of free alternatives to be found on YouTube, blogs and specialized sites on the Internet.
Pro A cheaper, standalone version called Photoshop Elements is available
A stripped down version of Photoshop, called Photoshop Elements can be bought as a standalone application for $100.
Pro Includes powerful content-aware tools
Photoshop includes content-aware tools such as content-aware fill that can fill in a select area based on what surrounds it.
Pro Packs a staggering amount of functionality
Photoshop is the most fully featured image editing software available today allowing you to perform highly advanced image manipulation.
It has tools for RAW image adjustments, lens correction, retouching, image stitching, HDR, fixing framing. It supports most professional color modes and file formats. It includes extensive lists of filters, styles, effects, fonts as well as tools for painting, sketching and typography work. It understands both raster and vector graphics. It even includes tools for video editing, working with 3D objects and support for 3D printing.
Pro Integrates with Creative Cloud
You can save all projects directly to the Creative Cloud allowing you to access them from any device and with any relevant Adobe software.
Pro Creative Cloud Photography subscription includes Lightroom
Lightroom is another image editing software from Adobe that's specifically designed for photo editing and managing of large quantities of digital images.
Pro Mobile companion apps available
There's a free mobile app available for iOS, Android & Windows Phone.

Pro Color selector with different color systems
RGB, CMY, HSB, and a somewhat different HUSL.

Pro Offers color ramp generator
Pixly offers a color ramp generator that then exports directly into a custom palette.

Pro You can use reference images
You can work with a reference image on top of your art, or by its side.

Pro Allows you to continue your work even when not in front of your PC
This tool works on both phones and tablets that run Android, which is handy for when you do not have access to a PC.

Pro Layered projects

Pro Gestures that feel natural on touch screens
In Pixly, you can move the art around with two fingers (like in Google Maps) and change the brush/eraser size with a three-finger pinch.

Pro Supports onion skinning
Onion skinning is also called ghosting. It allows the user to see the past and previous frames, while editing the current frame. This way, the user can make decisions on how to create or change an image.

Pro Mirroring support
In Pixly, the user can make symmetrical art with a mirror, or even go bananas setting up two or more mirrors at different angles at once.

Pro Transparency support
The user can make transparent sprites in Pixly.

Pro Animation support
Even though this is a mobile tool, it's fully featured and even allows you to create animations.

Pro Standard and custom palettes

Pro Live image tiling
The user can create tiles in Pixly and keep an eye on progress in real time.

Pro Color filters
Cons
Con Expensive
The standalone version of Photoshop costs $19.99/month, though it can be leased as part of the Creative Cloud Photography bundle that includes Lightroom for $9.99/month.
Con Latest versions of Photoshop are subscription-only
While you can still buy CS6 from 2012 without needing a subscription by contacting Adobe support or the cut-down Photoshop Elements, any full-version version of Photoshop past CS6 requires a subscription.
Con Learning it can take some time
While you can relatively quickly learn how to perform a few basic image editing tasks, understanding Photoshop's ins and outs can be difficult. It's partially due to the sheer amount of functionality that Photoshop packs (and understanding that some of the advanced functionality can take a while to understand on its own), and partially due to it being aimed at professionals with little hand-holding for novice users.
Con Very slow
It needs a very power CPU and GPU and many GBs of RAM and still it is so slow.
Con Stop paying, it vaporises
With Adobes adaptation of the "subscription world" PhotoShop too is available as subscription software only. This means it will never become yours. And if you stop paying, you won't have any PhotoShop any more. Whether you are OK with that or not, it also means that PhotoShop for a large part becomes software for those "who can afford it". Or "push cost to others". Like customers of professionals. Which is also a way to become an "industry standard".
Con Affinity Photo is just as good at a fraciton of the price
Switching from Photoshop to Affinity Photo and it's hard to notice the difference quality of a professional's work. They say that PS is the industry standard, but so very few pros that tried Affinity Photo ever look back.
Con Not good enough to be so expensive
Probably the only big advantage Photoshop has over the other free software is the adjustment layers. But still too expensive for just one feature.
Con Batch editing of images is not straightforward
Photoshop is designed to work extensively on one image at a time and while batch editing support exists, it's not that intuitive to use.
Con Asset management capabilities are lacking
In Photoshop asset management is done through a separate program called Bridge. As Bridge is supposed to be a file management tool for not just Photoshop's files, but for files generated by all of Adobe's applications it covers a breadth of capabilities, but not depth.

Con No PC version
The PC version has not yet been released.
