If your Mr Steam control has an aroma button on it, you might want to go with Mr Steam.
If you do not have the Mr Steam control with an aroma button, then you would have to install a separate control for the aroma pump for Amerec, Mr Steam, Steamist and Aromamist.
The pump that has a leading edge is the AromaMist model AI-5. For residential & commercial installations, this pump is solid and has been in the field longer than the other manufacturers.
Here is more info on AromaMist AI-5