Oh boy. Well. This is an incredibly geeky question.
The Daleks have the advantage of being the ultimate killers, while the Borg are the ultimate adaptors.
Could a Dalek beam pierce a Borg shield--particularly after they learn to adapt to it?
Inversely, could the Borg assimilate the Daleks through their casings?
Let's assume yes to both.
The Daleks could swarm the Borg with sheer numbers and killing rage, but the Borg could, just as easily, assimilate the Daleks to create Dalek-Borg--a truly terrifying prospect. I think that the Dalek-Borg would be superior to both and would wipe them all out.
Let's assume no to both.
We hit a standoff. The Daleks can't use their killer beam to attack the Borg, and the Borg can't assimilate the Daleks. Either they make a truce of some sort (doubted, knowing the Daleks) or they just sort of ignore each other. OR, and the most likely option, they start figuring out ways to kill each other--and by they, I mean the Daleks. They're clever bastards, and could probably sabotage all sorts of things on a Borg cube.
The Borg will assimilate and if they can't, then they will flee.
So I guess the Daleks win in this scenario.