I agree, the polyurethanes seem to stay green longer but when they do reach full cure they are harder to buff IMO. Like Barry has said a few times here, mix ratios can somewhat be an indicator of quality, 2-1 and 3-1 clears are usually higher quality than the 4-1 mixes. It's all rocket science IMO

, but if anyone wants to shed some more light on the subject I'm all ears.