Which would win, in a battle?
Defiant. It's overpowered, overgunned, and designed to take out Borg Cubeships. It's a pure fighting machine, as opposed to Voyager.
But Voyager has those "advanced" shields and weapons!!
To Moderator:
Can a board entitled "Star Trek Weapons and Worf-air" be created in the Trek Sink for these discussions and have all posts of "who would win" be place there?
These topics are legitimate, but I think they are too small to individually go in every Series board.
I'll have to go with the Defiant.
Defiant, shes a warship while the Voyager is largely a science ship.
Well, that's what the early episodes say, but come on here: Voyager has 13 type-10 phaser arrays and 4 photon torpedo launchers. The Enterprise-D (in docked configuration) has only 11 phasers and 2 torpedo launchers. And later episodes like "Equinox" imply that Voyager has a pretty superior tactical ability.
Nevertheless, I think the Defiant would win because:
1) it's more manoeuvrable
2) its weaponry has a higher BILC factor
3) Defiant has Sisko (or Worf, or Dax). Voyager has Janeway. 'Nuff said.
Polls Voice, my suggestion is to post that request in the Kitchen Sink. I'm sure Kerrie will be happy to oblige!
Plus, the Defiant has the Cloaking Device, but isn't that a VIOLATION,
of the Treaty with the Romulans.
No. The Defiant's cloak is Romulan device, with permission of the Romulans. Originally, there was a Romulan on board to work it.
Whatever happened to that concept, anyway?
"The Enterprise-D (in docked configuration) has only 11 phasers and 2 torpedo launchers." Thande
Actually, if you count them, 1701-D has 12 phaser banks.
Whatever happend to the phasing-cloak recovered from the USS Pegasis? That sure would've come in handy in a warship.
Inblackestnight: No, there are only 11, plus another one on the cobra head of the battle section which is normally concealed in the docked configuration.
They are:
1 x Upper saucer
1 x Lower saucer (both big ones)
2 x neck (small ones)
4 x right at the back of the stardrive section (small ones, above and below)
2 x at the base of the nacelle pylons (medium sized)
and 1 on the belly of the stardrive section (medium size).
I apologize Thande. Although it was sent at a later time, I was repeating myself with an Enterprise-D vs. Voyager, which only noted ten phaser banks, being docked wasn't an issue. Doesn't the tech manual say that Galaxy class starships have three photon torpedo tubes? I know it said it was in the saucer section but if it isn't in the captain's yacht or the main shuttle bay I wouldn't know where it would be.
That's okay Blackestnight. 
As for the third torpedo tube, it's in the saucer section but it's within the area normally blocked by the stardrive section's 'cobra head' in docked configuration - so it's rear firing. According to the Tech Manual it's designed to defend the Saucer from pursuit when the stardrive section is away.