They'll definitely be fighting back and forth for the top spot along with Wrecking Ball.
I have a feeling Katy will come out on top thanks to Roar's slayage but I'm rooting for Britney.
I think "Dark Horse" will get to the top first but will also be really front loaded in sales so "Work Bitch" will quickly pass it. Promo singles never have impressive longevity on the charts, Maybe Katy will change that? It'll be interesting to see. There's a lot of hype for both songs & I'm dying to hear them both.
I'm not a fan of Katy by any means and the snippet I heard wasn't even that great-sounding, but "Work Bitch" sounds like it's going to be a trainwreck based on what little we've heard about it.