Voyager would unfortunately win. The assault phaser would demolish the smaller ship with or without its fancy armor but an Intrepid class would be easily able to stay out of the small cone of fire that weapon had unless it was trying to escape or was fired on first.
The battle would hinge on Janeway's future tech torpedoes which seemingly cut through defenses like a hot knife through butter.
If not for the torpedoes the Galaxy would win. It has superior phaser power, endurance, a cloak and would chase down the smaller ship with its warp 13 speed.