Neither are particularly relevant, although Nicki should be ahead by miles with her latest stunts on Twitter and at the VMA's. That will change once AHS begins. Gaga has more positive attention than Nicki now and in general, so it doesn't matter who the GP is hearing about more right now
Nicki, easily. She's a household name and is still the biggest female in rap music. Gaga isn't anywhere near the top of her genre (Rih, Katy, Taylor, Bey, Adele, and Miley are above her).
For everyone saying Nicki: can any of you answer why Gaga's Jazz collaboration album sold more than TPP, even though Nicki performed at 2 VMA's in a row, had 2 top 5 hits and a string of other top 20's to promote, in a year when rap albums are some of the highest selling? If you're going to say it's because of Tony Bennett then please check the iTunes positions of his current album before coming at me.