WeChat is a free
A similar alternative to Messages
For those that don't like being locked into Messages, WeChat is a simple alternative and includes individual and group messaging features with text and emoticons. For group chats, you can use the Live Chat feature into which you can invite people via your own invite into the chat using QR codes. WeChat also saves your chat history so that you can search it at any time.
As yet, there are no video chat or multimedia options. Although WeChat is free, it doesn't invade your chats with intrusive advertising.
Messages style interface
The interface of WeChat will be familiar to anyone that's ever used Messages. Contacts are listed along the left hand side and on the right, you've got the main chat window. The chat window is at the bottom of the screen where you will also find a range of emoticons. The Chinese developers have clearly taken their inspiration from Messages and the overall usability is very similar.
No major advantages over Messages
If for some reason, you don't like using Messages on your Mac or mobile device, then WeChat might appeal but it doesn't offer any major advantages.