Given that the A330 (and 737) sims are in MEL, I would guess a choice of MEL would lead you towards the A330.
A330 would probably be quite good as a S/O as once it gets going internationally, there will be lots of sectors to try and get your hands on. And, if you can get in early, you'll have instant seniority in rank and could pick your trips.
Little or no overtime though.