One of the biggest difference i would i say is that:
3200 = no 6.2 Firmware unless you do ram upgrade
3200mx = 6.2 firmware ready :)
Thats why you see the diference in ram... its because it need it to run 6.2 version... and of course you should be needing it to run the newest 6.3 version coming, which is the only firmware that suppport ac APs
Cheers
Carlos