The HUGE advantage of the old G2 is that you can Lego it just like a 6P. It will take ALL the same bezels that fit on a 6P as well as all tailcaps. It can be fitted with UCL glass lenses and take any drop-in intended for the 6P, as long as one keeps the output within reason with the standard G2 plastic bezel. You can install any SF metal bezel intended for the 6P and run any drop-in you want. The G2 is actually a great host for Lego builds, here are two of mine;
The WML is fitted with a Surefire M2 Z32 shock bezel (ebay) and an EDC Plus X60LT P60 XP-L Hi V3 drop-in (560 lumens, 18k candela), fitted to a rail section using a Vltor SMOCG Scout Mount Offset CG. The light goes on and comes off quickly, so I don't have to have it mounted when not needed, or if I need to use the light as a handheld. The tailcap can be backed off to prevent accidental activation, and the total weight as shown with mount and two CR123 lithium batteries is seven ounces.
The G2 below has been fitted with a Malkoff M61LL drop-in (100 lumens) and will run for over 10 hours on a pair of CR123A lithium batteries. I also updated the plastic lens with an UCL glass lens, and the light rides very nicely in a KyTex horizontal holster.
Another point about the G2 is the plastic body is comfortable in the hand, is easy to grip and does not feel as cold in winter weather as a metal bodied flashlight.
With the WML mounted and the second G2 on the belt, I have effective and durable lighting that shares components and batteries. What's not to like?