Best bomber? Sekhmet, bar none. It's nearly as tough as an Ursa, has excellent secondary capacity, and its combination of good gun placement and decent maneouverability makes it a passable dogfighter as well, which is important for a gauntlet. In fact, in my opinion it is the best bomber, period, regardless of whether one is playing a gauntlet or not. Weapon picks: Prometheus S; 1 bank of Harpoons, 2 banks bombs.
Best fighter? You left it out of the poll - It's the Erinyes. Reasonably fast, reasonably maneouverable, reasonably durable, and packs one hell of a punch with primaries, while retaining as much of a secondary capacity as you can reasonably expect to go through on a single respawn. For other types of missions I'd usually want something with more secondary capacity, but for gauntlets, anything more than what the Erinyes has tends to be wasted. Weapon picks: Either Prometheus S + Maxim or double Prometheus S; 1 bank of Harpoons, 1 bank of Trebuchets.
I love the Prom S for gauntlets due to the insane range on the thing. You often end up in head-to-head passes and being able to get off 3 volleys outside the range of the enemy's guns more than makes up for the slight damage loss compared to the Kayser.
[Edit] Added which weapons I'd use.