Well, I have smoked most strains and I think they vary, even the same strain, so it's hard to isolate a favorite. I personally prefer a very sweet taste, with a up type high.
I have no doubt that the kush strains have the most THC in them, and I did make a post to a kush thread a day or two ago.
However, this year I had some kush that is absolutely the strongest bud I have ever smoked in the past 40 years that I have been smoking, and it's the nice up type high I prefer, so I have changed my position on kush. A couple years ago I had some kush that just hammered me into a state where I would start to get a headache, and I didn't care for that. But the latest strain I have smoked is entirely different, I'm not sure if it is crossbred or not. Other than that, all I can say is the boys in Garberville rock and grow the best weed in the world, IMHO, the home of the donkey-**** buds...lol
With that said, I often ask for sativa, but nobody has grown it that I know of for some time, as it doesn't have nearly as much THC in it, so most people I know grow Indica. Since kush is a strain of Indica, I would just say that Indicas are the best strains. The reason I would ask for Sativa is that I always have memories of how sweet Sativa is, but as I note here I believe that Indica can and is as sweet, and the latest strains of kush have changed my mind as they aren't that hammer you in the head til you got a headache type high.
What it gets down to is this...
"Dope is better in times of no money, than money is better in times of no dope..." - Freewheelin' Freddie
Or to put it in better perspective, "it's all good!" ;-)