I've been happy with SMC. If I were in the market for a new battery I'd go for 5000mAh 40C, but stick with major brands.
An important consideration I've run into is the charger. I switched from a charger that could only charge a 5000mAh battery at 1/2C (2.5A) and upgraded to a charger that could easily charge at a 1C rate (5.0A) and the battery seems to deliver a noticeable amount of more power. I went with the Duratrax ICE charger which recently has seen a price drop. The only bad thing about this charger is it charges at 8A max. So you basically can't charge a 5000mAh battery much over 1C, but I'm not worried about that myself.
My point is though, the charger does make a difference.