My vote is for Voyager. It did take on the whole delta quadrant by itself, survived 7 years of isolation, and fought some bad guys that were way bigger and better than it.
The problem with using Voyager as an example is that it's the hero ship of the series, therefore it's got to survive, so regardless of what's thrown at it, it will surive all TV episodes.* The fact we don't see any others of her class in action hinders a fair comparison even further (or even seen externally for that matter, though I can't remember if we get an exterior shot of the Bellepheron in DS9 to confirm it's an Interpid class).
The exselsior? Alot got blown up in the dominon war.
Sure you're not thinking of the Miranda class there?

I remember them blowing up a lot more regularly in TNG and the Dominion War.
A fair number of people died on Voyager. Most ships can't seem to get hit heavily without losing someone. And in defence of the Enterprise-B, half of it seemed to be missing during that incident
And just because it's a bigger ship doen't mean it has a bigger powerplant.
True, that it's not the automatic case, but it would be bad design to leave a ship underpowered when it's possible to give it better.
Voyager is rated for warp 9.975. It's warp core is powerful enough to get it there. The exselsiors can't hit that speed. Not by a long shot. According to one site, 8.7
Memory Alpha has no reference for a maximum stated warp speed for the Excelsior, let alone one as seemingly low as 8.7. What's your source here?
*The only exception to hero's ship immunity is the original Defiant, and even that was replaced in short order.