For reaching the "fat burning zone" ghee might be better... but for health and longevity, it's butter for the win.
I would go for butter since ghee has appreciable amounts of oxidized cholesterol, which unlike casein is probably actually bad for you.
EDIT: From experience on this site, I know I will be down voted into oblivion for disagreeing with the herd. So, here's my evidence: http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2887%2992443-3/abstract
I suspect Ghee is better, since it's got the water and gunk removed and is a purer source of fats. However, in my opinion, unless you're guzzling down bottles of the stuff, you're probably not going to see much of a difference.
ghee is amazing. don't believe that whole oxidized cholesterol deal. if that were true, cooking eggs in butter would have been a mistake for all these centuries. i just don't buy it.
but i think you should consume plenty of both. first of all, if you are getting raw grass fed butter, it's gotta be from organic pasutres from socal, which is the only company i know that makes it. i had a tub of it in my hand the other day, and i just couldn't justify $12 for one pound when i can get one pound of organic valley's pasture butter for $6. not sure if the 'raw' factor is worth twice the price. but if you do buy the raw, certainly don't make ghee out of it. that would be pretty silly. lol.
I have suspected for a long time that ghee contains oxidized cholesterol, so I was glad to read the Lancet article. I currently have a very expensive, half-used jar of grass fed ghee...which I am going to throw out. Compared to a fresh stick of butter, the smell of ghee is closer to that of a rancid fat. The homemade stuff might not be as processed at the commercial ghee, so less harmful. BTW, my Indian friend says ghee can be properly made ONLY with unsalted, uncultured butter.