Read QFIT's SuperSCORE comparison of most systems. I'm using Halves which is a very strong count for multiple deck games. It has a BC of .99 which is a major factor to consider in playing 4/6/8 deck games and makes very little to no error in estimating advantage. Also, it's the best count without a sidecount. I think sidecounting Aces during shoe games makes very little improvement to your overall advantage, but I could be wrong.
The deeper the penetration the stronger Halves performs.
(The system seems complex at first but if you are dedicated enough the addition, subtraction, deck estimation, and true count conversions all become easier. Practice makes perfect.)