Burning man, because there's more variety of musicians and acts. Sensation is mostly Trance, House, Techno, but Burning man has more genres and eclectic mix of music.
Burning Man is 50k people from all over the world. It isn't just music, but there is music 24/7. There's hookah lounges, plenty of open bars, sex theme camps, video game theme camps, art theme camps, punk theme camps, even a theme camp for kids set away from all the commotion. It is a festival of culture. And the VERY BEST PART of Burning Man has got to be NO VENDORS ALLOWED! Thus when you go to a bar, you don't need to start a tab. When you get a massage, you don't tip.
You're strongly encouraged to offer small, large, or artistic gifts, but participation is the primary goal.
PLEASE READ THE GUIDEBOOK on the burning man website if you DO INTEND to go. Too many people show up without reading it and it turns out to be a horrible week for them. MUST read!!! Honestly, if you go and you haven't gone before, it will BLOW your mind in either the best or worst kind of way. EXPECT to wait in line for hours--up to six, both going in and coming out (unless you enter late and leave early). There is just one small road in and out of the burn. It's an adventure, but IF YOU COME PREPARED it is WORTH the wait!