Most of the bombers are pretty sweet.
Broadsword, Crossbow, Longbow, Devastator - all have awesome forward firepower, which I love.
The Shrike, however, gets my vote as worst bomber. It was the only Prophecy ship in which I was actually concerned that the bugs outnumbered us 10 to one. The only 'useful' weapons were the charging mass drivers, which while sweet when attached to something fast like a Tigershark, aren't as effective with a slow cow like the Shrike. Give me the Devastators Plasma Cannon any day.
p.s. on a not entirely unrelated topic, who else would like to see a strike fighter built around the Plasma Cannon - no Torpedos, no other real weaponry, just a BFG and the speed to deliver pain fast.