When comparing Messenger vs WeChat, the Slant community recommends Messenger for most people. In the question“What are the best messaging apps for Android?” Messenger is ranked 21st while WeChat is ranked 44th. The most important reason people chose Messenger is:
Allows communicating with anyone who's a friend on Facebook.
Specs
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Pros

Pro Uses Facebook friends to create a contacts list
Allows communicating with anyone who's a friend on Facebook.
Pro Read receipts
Can see who has seen each message in group messages.
Pro Easy to share posts from Facebook
Integration with Facebook makes it easy to share any interesting posts from the Facebook timeline.
Pro Great UI
User interface of the application is clean, intuitive and easy to overview.
Pro Friends can be added by scanning a QR code
WeChat generates a QR code for each user that other can be scanned to add them as a friend.
Pro Can be used as a Walkie Talkie
WeChat has push-to-talk functionality that can be used both one-on-one and in groups.
Pro Large collection of animated stickers
Pro Easy to send voice messages
Users can record a voice message from within the app to then send it to a recipient, who can then play the message from within the app. It is all self contained.
Pro Enables meeting new people
WeChat has a feature that pairs random people for a conversation. It is activated by shaking the phone (requires location sharing to be enabled) and will present a list of people who are doing the same and how far away from you they are.
Another feature for meeting new people is the Friend Radar that will display people in your vicinity that can then be added to your contacts list.
Finally, there is the People Nearby feature which allows you to send and receive greetings from people in your vicinity.
Pro Moments social network is seamlessly incorporated
Pro Flexible creation of chat groups
You can create chat groups for up to 500 people.
Pro Filters for photos
WeChat includes a collections of filters that can be applied to photos to change how they look.
Cons
Con Lack of privacy
Messenger is owned by Facebook. Based on their privacy policy, this means that any information you provide (including messages sent) are used by Facebook to profile you and sell access to your data to advertisers.
Con Lack of end-to-end encryption
Secret (end-to-end encrypted) chats are only supported in one-to-one messages, and are not enabled by default, and the encryption has not been verified independently.
Con Notifications get muted after inactivity
New message notifications stop getting pushed if the application isn't opened for some extended period of time (seems to be around a week or so)
Con WeChat complies with China's requirements to hand over data
Con Conversations and chat groups aren't ported to new devices
Messages are stored on each device, so shifting to a new device means losing all the previous conversations, as well as an inability to post in previous chat groups until someone else posts there and you're alerted of a new message.
Con User base outside of China is comparatively small
While WeChat has over 400 million users the majority of them are in China. Adoption in other markets has been slow.
