There is nothing special about the Vasari fighters and bombers, except that they operate in small squads and are individually strong. This means that they can shrug off a flak burst or telekinetic push, but will be horribly owned by Magnitize. For the Advent the opposite holds, for their fighters will get instagibbed by flak burst lvl. 3, but they don't mind Magnetize very much.
As for fighters vs. bombers: like has been said, fighters are more valuable early game because they shred LRF and siege frigates and of course bombers. Bombers are mainly useful vs Capital ships, structures and Heavy Cruisers. Those aren't the biggest threat early game, so you shouldn't get bombers early.