The biggest difference betweeen the two is the VF is rear exhaust which means that it will be mounted different on the plane. If you have a tuned pipe on hand then the VF will give you great performance. With a Macs muffled tuned pipe (NOT a silent pipe) you could get upwards of 15,000rpm with an 11x7 prop. There's no way a stock 50SX will ever turn an 11x7 that fast.