the only difference I noticed was about the tailcap switch (momentary) : on one G2 model, the switch seems to be less ... smooth (?) than the one on the 6P. Is this due to the material used or is it a manufacturing defect ?? ... no idea
The G2 uses a completely different (inferior IMO) switch design than the 6P and the G2Z. As a result, the G2 isn't water resistaint where the G2Z and 6P are.
-john