Right now the top batteries for racing are made by IB the 4200 and 3800. IP has good cells too from what I have heard. GP was on top when 3300 and 3700 were still around. GP hasn't been producing racing grade cell for about 2 years now. There have been several players over the years and sanyo used to be on top when NICads were the only choice(1200,1400,1700,2000,2200,2400). Sanyo tried the NIMh game and lost big time with poor cells and less than desirable voltage and poor durability. Panasonic made some of the worst cells with 1700 and 3000.
Technology for some has passed them up while others like IB and IP have been able to produce an R/C grade cell that can handle the high charge and discharge rates plus the voltage demands for all those racers.
As different brands of cells were introduced they had characteristics that made them more favorable: runtime, voltage, lower internal resistance, price, life span, consistancy. GP (Gold Peak), IB (Intellect Batteries), IP (Infinite Power) and a new brand EP (East Power).