I have both, and the GSP Spit is more stout and looks much better with airbrushed matt camouflage, recessed panel lines, and rivet details. The GSP Spit is an excellent flyer with a YS 110 and doesn't drop a wing at low speed. The rear stab on the WM Spit is flimsy and tends to crack at the fuselage join. The elevator halves on the WM Spit are prone to flutter because both halves are being controlled by a single pushrod and a joiner wire. Mine would flutter at full throttle even though I have no play in the clevis. The glue on my WM Spit came undone at the firewall once, so I had to glue the firewall back in. The fuselage on the WM Spit is boxy and doesn't have wing fairings built in. The fuselage on the GSP Spit is nice and round with nice wing fairings. The vertical fin and rudder on the WM Spit are thin and flat. The vertical fin and rudder on the GSP Spit have airfoil shape. Overall, the GSP Spit is higher in quality, and fit and finish are excellent.