most efficient lehner

what is the most efficient lehner setup i could use in a rustler with 3s or 4s lipo? i already have a basic 4200 and its great but im building another rustler up and i need another motor and controller. i will buy the mgm controller since it has the lipo LVC so i dont have to deal with an in line LVC like i do with my bk controller. im really interested in the xl series but would they give me better runtimes than the basic series? i would prefer running 3s lipos but if its necessary i will go 4s for efficiency. thanks.