APX or P320... That or a metal frame gun. Everything else is really no different than a Glock. HKs, Caniks, M&Ps, CZ P10s, etc are just Glocks with a more complicated design, more parts, look/ergos, but for the mist part exactly the same.
IMHO, the APX is better than the P320, but the P320 does have more aftermarket support. If you're in the Gucci camp, that means something, but if all you require is a holster and different sights, thecAPX has that covered.
I own Glocks and the M&P 2.0 Compact. Not much different except the M&P 2.0s have more parts, are harder to completely strip down, and you fucking have to remove the rear sight to completely break down the slide. That's a pain in the asses if you want to install a APEX trigger or break down the slide for detail cleaning. With the APX at lease, with a $12 part swap, you'll have a somewhat simular trigger pull weight than with the APEX trigger.
Going from a Glock to a M&P 2.0 is NOT going to give you a different experience.