But 99% of people that buy the RS do not give a **** about shaving .3 seconds off a standing start, or getting the power down .2 seconds sooner out of a corner.
4WD isn't that fun to be honest, sure it can be faster, but that also means you need to be travelling faster to get the same level of fun.
The fact that they have similar lap times says it all to be honest, regardless of what weight advantages the Focus has. That said, none of these cars prospective owners will ever pilot them that quick, in fact, I bet only a fraction take them on track.