Let's talk about repetition in band names. Sometimes it is just tedious, as with The Yeah Yeah Yeahs. Try having a conversation or writing an email where you use their name more than once; if you're like me, you'll be tempted to call them "The Yeahs" or "The YYYs." It is an amusing name on paper, though.
Hot Hot Heat rolls off the tongue more easily. But what's really great about the name Hot Hot Heat can only be appreciated at one of their concerts. In the time between the end of the set and the encore, the audience started chanting "Hot Hot Heat!" It makes a really excellent chant, especially when synchronized with foot stomping. I haven't been to a YYY concert, so I don't know if the same thing happens there. If it does, it could redeem the YYY's name to an extent.
The Yeah Yeah Yeahs: 4.6
Hot Hot Heat: 7.0