If you can spring for it, buy F on the A319--especially if the flight is over 2-3 hours.

MCE is fine--rows 9-10 are best. Row 8 is okay, but be aware there's a bulkhead so you may not find it comfortable if you prefer to stretch out or be able to put a bag under the seat ahead of you.

Exit row has better leg room, but rigid armrests--not a big deal unless you're a "Person Of Size" since the seats are noticeably narrower.

Regular coach will be very uncomfortable unless you are under 5' 6" / 66" / 168 cm and fairly slight in build. I am neither of those things, so avoid A319s save for confirmed seats in F or MCE.

cheers and happy travels!