When comparing Hangouts vs MAPS.ME, the Slant community recommends MAPS.ME for most people. In the question“What are the best Android apps?” MAPS.ME is ranked 11th while Hangouts is ranked 41st. The most important reason people chose MAPS.ME is:
That saves a lot of download, e.g. from ~500MB in other applications it is reduced to ~50MB for German surroundings.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Save and sync your chats across multiple devices
Start chatting on your phone, then on your computer, then on your tablet seamlessly!
Pro No need to create a separate account if you use any other Google service
Hangouts uses Google account credentials. If you use any other Google service, then you already have an account set up.

Pro Group video support
If you have signed in your Google account, Hangouts allows making video calls with up to 10 people or one-on-one. There are business, education and government solutions that increase the participant count to for video calls to 15 as well as offers support for those accounts.
Additionally, you can switch between using either the front-facing or rear-facing camera on your phone or tablet.

Pro Free and cross-platform
Google offers all features of Hangouts completely free on iOS, Android and web with quick and reliable sync across all platforms. It's also tightly integrated in other Google services - it can be accessed from services such as Gmail, Google+, Chrome.
While the standard Hangouts offering is completely free, there are business, education and government solutions that increase the participant count to for video calls to 15 and offers support that may cost money.
Pro Chrome browser extension
Use the extension on any computer you can run Chrome browser to text from your computer or tablet!

Pro Excellent read receipts in group chat
It's possible to know what each and every participant of the group has read. Their icons are displayed below the last message.

Pro Can share animated GIFs
If you have gifs in your mobile phone, you can share them in the conversation and your partner will be able to see it animated in the chat.
Pro Google Voice integration
Google Voice is a service that enables making and receiving free phone calls within US. Google Voice forwards incoming calls to all connected devices and allows placing calls from any of the connected devices, but they will show as coming from the Google Voice number.
Hangouts completely integrates Google Voice, allowing you to place calls and receive texts and voicemail from all of your devices. The Hangouts app for Android also includes a needed dialer for making calls with the users Google Voice number.
Pro Free calls to US and Canada from anywhere in the world
Hangouts app for Android can be extended with an optional dialer for making calls. Most calls to US and Canada are free and international calls have cheap rates.
A Google Voice account will be needed in order have a number that allows these calls to be made.
Pro Advanced status sharing
Hangouts can inform about the status of other users including what device they are currently using, whether they are in the middle of a call and when were they last seen. This allows making sure that you're not disturbing someone when initiating a conversation. It's possible to granularly turn off status sharing.
Pro Video tools
Hangouts can add different effects and overlays to video calls that can be viewed on your device. Unfortunately, they can't be set from your phone.
Pro Seamless integration with OK Google for voice control and typing
Hangouts can be used completely hands free, even if the app is not open and the phone is locked: "OK Google, send a Hangouts message to Mary".
Pro Very detailed selection of areas to download
That saves a lot of download, e.g. from ~500MB in other applications it is reduced to ~50MB for German surroundings.

Pro Includes offline routing and turn-by-turn navigation
Users without a data connection can still use the app for turn by turn directions, which is great for those that travel or use a device that does not have a cellular data connection.
Pro Obtains data from community-based OpenStreetMap
MAPS.ME uses data from OpenStreetMap, meaning the data retrieved from that service is a community-based map. Anyone can freely edit and contribute to the map, a map concept that is similar to Wikipedia.
Pro Fast rendering
By using compression of the map data, MAPS.ME is able to speed up the rendering of their maps to one's device. This allows for a quicker feeling app.
Pro Optionally can download traffic information
And showing it color-coded (Google-maps-like) on the streets.
Pro Discover nearby feature
Shows a nicely organize list of interesting places to visit close to your current location.

Pro Matching modern material-like interface
The design of the app uses a material-like interface making for a close to native looking experience on Android.
Pro Offline vector maps
Automatically downloads vector maps for offline use.
Pro No nagging advertisements
Pro Easy to install
Pro Easy adding/editing of bookmarks/favorite places
Click on the map and you will have the option to Bookmark, Route From, Route To. Having selected Bookmark simply offers to edit it, e.g. give it a different name.
Pro Allows to edit OpenStreetMap data
It is possible to add new and edit existing POIs in OpenStreetMap database using a nice interface.
Pro Night mode
There is a night mode option.
Pro Integration with booking.com
Displays information from booking.com about hotels and apartments.
Cons
Con Transitioning to corporate orientation
Google is turning Hangouts in to a Slack competitor. It's unclear what the future of Hangouts is, but Google has said the consumer Hangouts we now have 'isn't going anywhere.'
Con Lack of end to end encryption
Communications are encrypted between client and Google servers but not from sending client to receiving client. This means that there is still a possibility for someone other than the receiver to read your message if they have access to internal Google servers. But it allows also lightweight chat history search, spam protection and other features.
Con Is owned by Google
Google is a cooperation that earns money from collecting data and breaching privacy.
Con Poor interface
The app tends to lag, the design can be confusing and considering that another app has to be installed that supplies another icon in the home screen in order to get a dialer for calls in Hangouts, overall it is very confusing and cluttered.
Con No rich text editing
On Android you can receive messages with bold or italic text. However, you cannot bold or italicize text on Android, only on iOS devices or via the web interface.
Con No way to moderate groups
If a member of a group chat room becomes disruptive, or there's some other need, there's no way in Hangouts to remove somebody from an existing chatroom. Similarly, if somebody is no longer active, there's no way to remove that user from the chat room to make slot for new active members.
Con Buggy video calls
Whether video calls work on your device is pure lottery, and there's nothing you can do to fix it.
Con Poor indication of who's online
There is no way to find out if a person in your contact's list is online or not in the Android app.

Con Poorly manages data
Doesn't cache images well either received or sent. Often users will see the sent images re-downloading, same for conversations.
Con API support was removed
This change closed options for integrations and connections between similar apps.

Con Not available on Windows Phones
There is no Hangouts app for the Windows Phone.
Con Doesn't support sending voice notes or video recordings
Currently there is no built in function that supports creating and sending voice notes or video recordings.
Con No customer support
Free product, you're on your own.
Con Won't send SMS/MMS anymore
They removed support for sms/mms. The same goes with integration to hangouts.
Con No SMS/MMS backup
They don't have options to backup sms to cloud.
Con SMS messages sent from the web app can't be sent outside North America
SMS messages sent from the web app can only be sent to number in America and Canada - sending to foreign numbers won't work, although you can still receive texts from anywhere.
Con Poor response time to recalculate the route
Con No option for satellite/aerial/topographic imagery
Not as useful for navigating while hiking/climbing/etc.
Con Very slow search and route calculation
Probably because MAPS.ME has more POIs in its database which ends up with all searches and route calculations being very slow.
Con No display of speed limit
Neither the next nor the current one.
Con No way to distinguish between fastest, efficient or shortest route
Con Very limited options
E.g. no way to hide certain buttons like the traffic button, or to configure the language used to display city names.
Con Sometimes very strange suggestions
E.g. when not using the suggested route, Maps&Me continues to request to turn even if you are more than 100m after the cross-road.
Con Favorites are a little bit too hidden
Because they are stored in groups.
Con Traffic information is not available in all countries and cities
Source of traffic info is a trade secret this feature is only available to some selected cities.
Con No lane assist
Con Being based on OpenStreetMap data can be lacking
The use of OSM also has the drawback of many places not getting the attention needed for updates. Depending on the geographic location OSM may have the most detailed maps or the most bare/outdated map.
Con Does not show images offline
Does not show images offline if supplied in standard kmz file. i.e. zipped kml plus image folder.
Con No tourist detail maps
