The R8's mid-engine layout doesn't give it an edge over the SLR
because despite being front-engined, the SLR still has a 50/50
weight distribution (that long bonnet helps here).
As for RWD or AWD, it's a matter of preference. If you love loads
of oversteer, RWD's the way to go. If traction's your priority,
it's AWD, but with almost twice the R8's torque, the SLR's not
going to be too bothered by that once grip kicks in.