You could attribute that to Miles being around for longer, but I feel like Kamala is gaining more traction faster than Miles did (I'd have to double check, so don't quote me on this).
Either way, while I do see Ms. Marvel as being more likely than Miles, there's still a chance for Miles to get in (as he almost made the cut for UMvC3).
It's hard to really say who is catching on faster and it also might depend on whether you're talking about just comic book readers and such. Regardless Miles definitely had the upper hand, Spiderman is a *LOT* better known than Ms. Marvel and when Miles debuted it was something big that was covered by the press. I could be mistaken, but I think Miles had an animated series too.