Rihanna vs Lady Gaga...Who is gonna last?

So I've been wondering about this for some time...Actually since this May. But it seems like there is a new pop diva battle going on and it involves the two biggest pop princesses of our day: the beautiful and exotic Rihanna and the talented and wacky Lady Gaga. Both play dance pop, both are extremely talented and both have an eccentric style. More importantly, they are both like Madonna in that they do dance pop that is darker and more artistic than say Kelly Clarkson or Pink. I just wanna know one thing: Who do you think is gonna last? I'm placing my bet's on Rihanna. She seems to have this whole thing figured out. If Lady Gaga continues to do the whole Grace Jones/Bowie/Madonna thing, I think the public will eventually get sick of it. Recently, Rihanna seems to be showing different shades of her character and reinventing herself in the way Madonna has. So what you you all think?