Well, I can't really say anyone's "better", because that's all opinion, but I will say that of the two, Gaga is my favorite. I don't have a problem with Kesha, but there's only one song of hers that I really like. I've loved all of Gaga's songs so far (except for Born This Way, but even that's an ok song...I just like the lyrics more than I like the tune n_n).
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Something I do like about Kesha though is that she writes her own music.