Punisher is the fastest, but it's not ROAR approved, the club in my area allows the Punisher, it's the fastest motor that money can buy for stock racing. Monster Max has been the staple of ROAR approved, but I think the X-Factor is the newest design, so I would assume it's on par with the Monster Max, but says ROAR Pending so the X-Factor may not be allowed if your club is stringent on following ROAR rules, if not then I would get the Punisher.