On the ATR go for Row 1, with specifically 1C being the best seat.

Row 1 is great as you get more legroom wth the bulkhead and exit. Beware of seat 1B, If the forward FA seat is broken they will comandeer 1B but you will not find out until you are onboard the A/C. Another key benefit is those seats are much quieter as you are sitting forward of the props. Seats in the back get LOUD. Yes, you do board the ATR from a door in the back so you will be last off, but IME it only takes a few minutes to disembark. I cannot comment on MIA bussing, I've flown them ex-SJU.