The WRE/SMS is restricted to 15bhp and has about 28 when you take out the restrictions.
The WR is restricted to about 6-7bhp(!) to meet co2 and noise requirements and puts down about 38 to the wheel derestricted.
The difference between the WRE and WR is gearbox, sprocket sizes, frame, suspension, cylinder ports and carb.
The WRE/SMS uses a 28mm Dellorto with TPS, the WR uses a 38mm.
Suspension is cheaper and softer on the WRE/SMS.