928 is a Verizon (CDMA) variant of the 920 with Xenon flash, a louder speaker and an AMOLED screen. The outer design is also different, more squared off with tapered sides. Other than that it is essentially the same as the 920. It has a fully unlocked GSM radio and Verizon's LTE bands
I'll buy a 1020 just for the camera, but assuming you're locked into Verizon, the 928 is your best choice.
Charging cases for the 1020 are quite rare, and the 1020 doesn't really improve much upon the 928 (aside from that delicious camera and lanyard strap)
My 820 came with built in wireless charging, I bought the Nokia charging plate, just lay phone on plate with flip case and it connects, charges as fast as plugging it in to charger. Jim