Versus the M5, it's not surprising at all. Any road race fans can tell you that around a typical road course, in rainy/wet conditions, AWD cars turn in ~6% slower lap times than when it's dry. FWD cars run ~12% slower, and RWD cars run ~18% slower. Kind of interesting the consistent spread between each layout. Now if we make things even slicker and throw snow into the equation, I estimate the difference would be even greater.