Reach vs IMO

Ability to send a single message to multiple people without exposing their contact information to each other. Reach sends individual messages to the group rather than starts a group chat.

When sending a message to a group of people, Reach starts a private conversation in your Messages, Mail or WhatsApp apps respectively for each recipient

Improve workflow productivity by creating reusable recipient groups

Reach does not require the recipient to have Reach installed on their device. Instead it uses the existing messaging apps on the device to send the message to the recipient.

Prepare message templates which can be reused. Message templates can have recipients name variable, for example the template "hey {first name}!" will be populated with the recipients first name when the message is sent out

Reach integrates with Google Voice and allows to send free text messages in the U.S.A and low rates across the globe

Using Google Voice integration, Reach is able to send mass texts in a fully automated mode (without the need to press "Send" button for each message)

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.

Tabbed chats make it easy to switch between conversations

Both your buddy lists and chat histories are searchable.

Concurrent sessions allow you to be logged in on your desktop while also being logged in on your phone.