I switched from CometChat to ArrowChat this week and so far I've been very happy with ArrowChat however one thing bugs me a lot which didn't occur with CometChat.
When you browse your website in multiple tabs the chatroom or 1 on 1 chat only sends messages to one of the tabs. This means you need to track which tab you originally started chatting in to prevent closing it and missing out on sent messages.
In CometChat it didn't matter what tab you were on you always received the same message across ALL tabs including the chatroom. The only way I can receive the messages is by doing a refresh in the other tabs.