Yeah, I'm going to have to give this one to the Borg. After all, the Cybermen's main goal (forgive me for being a nu-Who fan, as I'm basing this solely on what I've seen, their original purpose might differ) is to create a perfect form, which they believe they have. The Borg are still seeking such a form and believe that assimilating other species will aid them.
In a battle between the Borg and the Dalek, I think the Borg have a few advantages, namely their motivation. The Daleks would seek simply to exterminate the Borg, but the Borg would work to assimilate the Daleks. If I'm understanding the Daleks correctly, they were created to be the same, so all it would take would be for the Borg to assimilate one Dalek. After that, combining their power with the Dalek's they'd seek to, perhaps ironically, exterminate the rest of the Daleks, as they would serve no further purpose.
The Daleks would also be at a disadvantage with Davros. While the series four finale showed that the Daleks could subjugate Davros, if he were to be assimilated, the Borg would then understand how Davros created the Daleks, once again rendering their assimilation pointless. Maybe they wouldn't be able to control the Daleks, but they'd have the knowledge they'd need to defeat them.
Of course, it's all over if the Borg were able to assimilate the Doctor and his TARDIS...