All three Pearl models have the same functionality. Where you plan to use and install Pearl, and how many you want in close proximity will guide your decision.
For example, if you will be using Pearl at a number of events and plan to hand-carry or ship with a person (e.g. not freight ship), the portable model may be your best choice. Its included carry case makes it easy to bring it to your next event. If you’re planning to freight ship a portable rack, one of the two rackmount models is a better choice.
For fixed installations, space may dictate your choice. If you need two systems in close proximity and have limited space, Pearl Rackmount Twin is the perfect choice. For limited space when only one unit is needed, the portable model is smaller and may be just what you need.