Yamaheater with the boost module and you'll have the warmest handwarmers you'll ever need.
If you get the RSI heaters and grips, they might be a little warmer, or they might be the same.
The problem isn't the warmers, its the amount of power being supplied to the warmers. Unless your sled is wide open, it isn't getting full power. And at idle or low RPMs you get virtually no power to the grips. Yamaheater gives you full power = warm hands.