It all depends on personal preference.
Poorboy's is really good and natty's blue darkens the paint.
XMT is really nice and fairly new, and Souveran is awesome and makes paint look GREAT, but is also A LOT more expensive.
Both are good brands, but if I had to choose one, go with XMT/Souveran if you have the money.
I think Im gonna go with the pinnacle ,heard so manny good things about it and seen some really great before and afters ,there goes my paycheck .Thats ok though Im gonna sell my brother some speakers so I can afford my new addiction..lol