OAL matters.
A 32" trap single is about as long as a 28" 870.
Balance and weight distribution matter, and they can be tailored to a particular use.
A 32" Beretta O/U like Dave's is a fine-swinging, smooth gun, but it's a buggy whip compared to a 34" Perazzi trap single -- which is a wonderful trap gun, but utterly useless for anything but regulation American Trap. Even for Wobble, I wouldn't want to use it.
For an all-around gun, I'd personally lean towards something like a 30" O/U, but my 28" Beretta 12 Gauge shoots trap just fine, and everything else from Chukar to 5-stand. The little old 26" 20 Gauge O/U I bought used for quail actually works fine for trap, if you slow it down -- but it wouldn't be my choice for the purpose. And Beretta's 32" O/U's are still quick enough, while adding that wonderful smoothness to the swing.
If you can, try some guns.