RC level kit is great. Maintains the ride quality and the actually levels the truck. Angle on the UCA's changes minimally and the RL kit isn't worth the extra $.
I asked my truck shop and all their employees a million times haha! They agreed the RC kit is the way to go for leveling an AT4.
Here's mine fella's. 20' AT4 w/duramax.
2 in RC level kit. Falken AT- 295/60. Fuel Rebel 20" wheel. Minor rub on the felt liner at full lock. Don't notice it enough to even think about switching!! Haha. Stance and ride is great imo. RC level kit didnt mess with factory AT4 ride either.