the 4.5 is wayyy too much, but other than that, BL is the way to go, but u can allways turn down ur throtle input
i would say the 6.5, unless u plan on racing (grip)
and a BL 4.5R Would out run any other car, and be on the track longer, and most of the time the motor is super cool, we have run allmost allday on my Step-dads HV-MAXX (wich is 14. somehting volts) and there is Reedy, but they Neo 4 star is not as fast as the 4.5r