Recs.
Updated
SpecsUpdate
Pros
Pro It has more features at a cheaper price
You can store your files within Whaller in the "sphere box" which is a file manager. You can also use a Dropbox or Google Drive widget if you want. If you're a project manager, you can use the kanban board to manage your team and assign tasks. You can make it a portal or a corporate website a little bit like Sharepoint.
The interface is really intuituve.
Pro It doesn't lower your productivity unlike Slack
Slack and many other services that were originally supposed to increase productivity turned out to be worse than email because of notifications.
Whaller tackled that issue brilliantly with its in-group private conversations. It's simple : you can mention people within a group and decide that the message will only appear to them and not the rest of your team, thus, preventing them from being bothered by an undue notification.