Which would win?
I'd have to go with the Defiant since the Enterprise-D was destroyed soon after the former's commission.
She was destroyed because the Klingons were able to discover the shield frequency in Generations, and cause serious damage. Considering we saw how small the Defiant is next to the Enterprise-E in First Contact, I'd say D's firepower would overwhelm the Defiant, and win the fight. Any ship without shields would lose a fight.