For a short flight like this, I'm not sure there is a profound difference, but--as a matter of principle--I prefer mainline planes over barbie jets, except that the ERJ-145 has no middle seats.

In my opinion, if you're on a fulll A-320 (or 737 or 757, for that matter) and you end up with a middle seat, you probably will have a slightly more comfortable experience on an ERJ-145.

Again, though, on a flight this short, it doesn't make much of a difference.