The A seats are the best on any of the ER3, ERD, or ER4s. 1A is a bulkhead seat and has some extra knee room, but you can't extend your feet as far. Plus if you have a larger than average belly then getting that tray fold down could be a challenge in 1A.

Personally I favor the A exit row, then 2A, 3A, 4A, etc.