I wouldn't call it objective, but I've been using osx exclusively for 3 years now and shortcuts still come slower than windows, primarily because on windows I can press control and any key using just one hand by using my pinky for the control key.
Depending on where the control is on your keyboard (Windows vendors keep swapping FN and CTRL unfortunately, and rebinding might not be easy), I think the position of the hand is more natural - on the other hand, you might strain your pinky when pressing CTRL (or SHIFT) for long time and I haven't noticed that with using my thumb yet (and I doubt it will happen, given it is a much stronger finger).