I only have a 6P and a G2, which is the Nitrolon version of the 6P.
Same power. Same toughness. Cheaper.

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