Being larger does not make the ship more suited for battle. I might go with Defiant just based on maneuverability and the fact that it has a cloaking device.
Voyager with future armor, okay, but Voyager when it was built loses easily to Defiant.
I don't know why they never introduced the concept of fighters in DS9. They were rather obvious additions to Babylon 5 and BSG. Maybe they only didn't it because they were afraid to be accused of copying B5?