When comparing IMO vs IM+, the Slant community recommends IMO for most people. In the question“What are the best messaging apps for iOS?” IMO is ranked 19th while IM+ is ranked 23rd.
Ranked in these QuestionsQuestion Ranking
Pro Video call support
Pro Beautiful User Interface
Although IMO has a comparable, and in some cases superior, feature set when compared to the competition its key selling point is its interface.
From LifeHacker when it won "Best IM Client":
Signing on, navigating chats by tapping the tabs at the bottom, searching for buddies, and virtually any other operation is easy to find and use. The app, itself, is very quick. Even sending a voice IM, if you don't feel like typing, is responsive and sends quickly. Everything imo does it does well, but it's excellent navigation really makes it top notch.
IMO also has a fully functional website that you can use for chat while on your desktop or laptop. This really puts IMO ahead of the competition as you can use the same system on all your devices so you don't have to deal with overlapping notifications etc. (Note: IM+ also has this feature)
It should also be noted that it has the highest rating in the App Store due to both the UI and its stability.
Pro Easy to switch between conversations with tabs
Tabbed chats make it easy to switch between conversations
Pro Lists and chat histories are searchable
Both your buddy lists and chat histories are searchable.
Pro Accounts can be linked so you don't have to sign in to several accounts
Pro Push notifications
Pro Concurrent sessions
Concurrent sessions allow you to be logged in on your desktop while also being logged in on your phone.
Pro Chat groups
Pro Can send encrypted messages
IM+ has the most extensive client support out of any of its competition and is the only app with the ability to send secure, off-the-record messages.
Pro Simple user interface
IM+ does the core IM experience incredibly well. The layout is intuitive to use and the very high app store reviews indicate how stable and user friendly the app is.
Pro Advanced chat history
Access your messaging history in the app or on the web
Pro View Twitter feed
Pro Off-the-Record Messaging (As a paid upgrade)
Pro Group Chats
Skype, MSN, AIM, and ICQ only
Pro Photo, voice, video and IM messaging
Pro Web application to chat from your desktop or laptop
Pro Extensive client support
IM+ has the most extensive client support out of any of its competition:
- MSN/Live Messenger
- Mail.Ru Agent
- SINA Weibo
- Yandex IM.
Con No support for third-party instant messaging networks
On March 3, 2014, IMO will start discontinuing support for all third-party instant messaging networks.