The G2Z is a reliable and very sturdy light. The G2 (not G2Z) isn't equipped to deal with water where the G2Z is. I consider that a big issue. The G2Z also has a lock out tailcap and Pyrex lens which are nice features.

My understanding is the NRA version is the same as the G2Z version - it is really just a discount for being a NRA member. Note you will have to put in your NRA membership number in order to purchase (if you aren't a member you won't be able to purchase the discounted version).

-john