As grad students we love to debate the merits of R versus Stata (and it's quite fashionable to use R to "signal" how teched up you are), but it is a mostly pointless and nauseating discussion. If you have a clear hypothesis and you know how to properly specify and estimate a model of that hypothesis, that is what really matters. More importantly, BFB is right - you'll need to adopt whatever program(s) your various methods professors prefer anyway.
Just knowing what R is in the first place at least shows that you have a pretty good idea what grad school will be like. That's probably worth something.