I just swapped out a 1900ACv1 to the 3200ACM-RM2 (got a cheap refurb unit off ebay) and the differences in speed with the current builds is minimal with my 1Gbps connection. Testing both stock and LEDE. Even with a number of devices all hitting the router at the same time. The big difference seems to be signal strength. the 3200 (even tho its limited in hardware) - seems much stronger with higher connection rates.
The only issue I am having with the 3200 is I cant seem to change the channel of the 5Ghz - I have to set it to auto - which goes to channel 40.. even if i set it to change 40 manually - the interface doesn't come up. But - lucky for me - the 5Ghz routers in my area have all moved their channels since mine is so strong!..I was using a wifi monitoring tool at the time.