I have IB3800, IB4200 and GP3300, GP3700 and GP4300
First the cells need proper care, so:
1. don't live them totaly empty for longer time
2. don't discharge them under 0,8-0,9v per cell
3. don't overcharge them(heat is killer of the cells!) don't go over 50c-i have ice charger and temp. cut off is set to 46c!
4. always use liner charging
5. buy good charger
The best for me is:
IB3800 and IB4200 - only runtime is diferent.
then
GP4300
then
GP3700
I use them for mod. racing and for low turn brushless and brushed motors and this year i have newer kill a single cell yet(owner of 12x6cells packs all matched!)