Against even half competent team shooting down bombers aint so easy as you think. Time to kill bombers is so long that killing em gives good oportunity for enemy interceptors or what ever to kill you even before you can kill the bomber especially against empire.
First of all why should you play with only fighters or bombers when you can fly any ship at any point. But if you would have team full of bombers or fighters for what ever reason both of thous teams would perform poorly. One team would lack offensive power and other defensive power. Mix of all ship types is much better or using 1 type more depending on situation cuz you know you can change your ship during matches...
Why would you care about exp when you can get all upgrades open in under 80h and most of thous upgrades are useles anyway so about 40h of playing and you have all you need.
Btw interceptors don't have any anti capitalship weapon and fighters does not have even nearly as powerfull anti capitalship weapons compared to bombers neighter do they have hitpoints to survive capitalship attack like bombers do. Allso bombers do have anti fighter weapons that are really effective why not use them?