Well, to be honest, neither the Enterprise-D or Voyager ever really defeated Borg cubes on their own (Endgame future technologies not withstanding).
They both held out in a firefight with respective cubes on their own. Voyager even had a full blown battle with the Tactical cube (which could be stronger or far more combat oriented than the cube that attacked the Enterprise-D - the armor along it's hull certainly implies it being better protected) and was able to survive for several minutes before having to retreat.
In both cases though, neither ship was a match for their opponents, but given what we saw on-screen from their performance, they seem to behave equally in terms of firepower and shield strengths (Voyager only being handicapped in the torpedo department because it had fewer than a Galaxy class - but 36 is probably not it's maximum - I would surmise that it should be able to carry at least 50 or close to 100).
Aside from that... the Defiant could be on par with both of those ships in terms of firepower and shields - due to obviously lacking creature comforts or luxuries (Voyager can get away with having a minimal compliment of those due to it's size, but it would still be 'stripped down' compared to a Galaxy class - which is why it would be able to match it in weapons/shields and outclass it in Warp speed).
Aside from that... most new ships post Wolf-359 would likely be on similar footing like the Galaxy class.
And depending if SF sacrificed certain things in luxuries and creature comforts, then they could all well be on equal ground tactically (except in torpedo counts which would vary by size of the ship) and of course would excel at their designated functions.
They both held out in a firefight with respective cubes on their own. Voyager even had a full blown battle with the Tactical cube (which could be stronger or far more combat oriented than the cube that attacked the Enterprise-D - the armor along it's hull certainly implies it being better protected) and was able to survive for several minutes before having to retreat.
In both cases though, neither ship was a match for their opponents, but given what we saw on-screen from their performance, they seem to behave equally in terms of firepower and shield strengths (Voyager only being handicapped in the torpedo department because it had fewer than a Galaxy class - but 36 is probably not it's maximum - I would surmise that it should be able to carry at least 50 or close to 100).
Aside from that... the Defiant could be on par with both of those ships in terms of firepower and shields - due to obviously lacking creature comforts or luxuries (Voyager can get away with having a minimal compliment of those due to it's size, but it would still be 'stripped down' compared to a Galaxy class - which is why it would be able to match it in weapons/shields and outclass it in Warp speed).
Aside from that... most new ships post Wolf-359 would likely be on similar footing like the Galaxy class.
And depending if SF sacrificed certain things in luxuries and creature comforts, then they could all well be on equal ground tactically (except in torpedo counts which would vary by size of the ship) and of course would excel at their designated functions.