Choose Pro 2 Next Generation if you want to try air pulse technology for the first time, only want pressure waves and want to keep the cost down. It is also about 30 grams lighter than Generation 3.
Choose Pro 2 Generation 3 without the app if you want both pressure waves and vibration, want to be able to remove the cap and clean the chamber and want to charge with USB-C, but do not need your phone.
Choose Pro 2 Generation 3 Connect App if you also want remote control, custom patterns or music control.
Choose Pro 2+ if you want two motors in a smaller and lighter body and can live with a magnetic cable and no Liquid Air cap.
If fit is the deciding factor – if the opening on a previous air pulse toy did not seal properly – none of the Pro 2 models will help, since none comes with a different head size. In that case a model with heads in several sizes, such as Womanizer Premium 2, is a better choice.