Hello Kris,
easy question - difficult explanation ...
The biggest difference between these is 802.11 standard used
AP6522 is an 802.11an AP with MIMO capability.
AP7522 is an 802.11ac AP with 2x2:2 MIMO capability
In short - AP7522 will offer much higher throughput speed comparing to AP6522
Check specification sheets for both for more.
AP6522 vs.
AP7522
There is a lot more these APs differs at, but I believe this will be the decision maker for you.
For EOS dates, check our GTAC KB and look for article
When is the "end of service" date for the AP650, AP6511, AP6x21 and AP6x22?
Imho - AP7522 will be better choice.
Regards,
Ondrej