It's a question about a good deal more than conventional technology and firepower. It's also a question about themes, and lessons they might try to instill on us.
In their respective universes, the Orks can be a high level threat if given attention, but more often than not play a second fiddle to Chaos or Tyranids. Daleks, conversely, are invariably the most dangerous and perilous force in any story they emerge, putting fear into all other races - even the Time Lords.
Doctor Who is a show that's all about smarts, cunning, weird plans, and ultimately, peace and better future. Daleks exemplify this: nothing has ever beaten them in a direct show of force
Warhammer 40k, meanwhile, is a dark scifi parody with its roots in 2000AD and many other darker stories of the time. Its lessons, if it has any at all, would relate to the cruelty of the world and how sometimes you just need to laugh at it. Orks are the closest thing passing as a comic relief in this world, and the only thing you can do about them is to kill them all and burn the spores.
If the battle takes place in the setting of Doctor Who, taking up on that show's themes, then the Daleks are certain to win. They'll come up with some bullshit to deal with anything Orks can throw at them, and the only hope the greenskins have is if the Doctor shows up as well to save them.
If they fight in the 40k universe, Orks might have a good shot at winning, because they're funnier and have an actual personality and something they satirize, while the Daleks are basically just another set of metal Nazis for them to beat around.
On neutral ground, though, I'd say the Daleks have superior technology, enough to beat back the vast numbers of the Orks.