I have handled a g2z as well as a z2. I walked away with a g2z. Why? My reasoning is close to Quasar's: lighter, more durable for carry, pyrex lense, its black and mean looking (lets face it - in cpf this is a must consideration /ubbthreads/images/graemlins/cool.gif ) and when I drop it it wil give me more shock absorbtion than its z2 equivelent (not to mention it won't ding and scratch anywhere near as much) due to its light weight and slight flex. Both have excellent combat grips, but the g2z will probably be better to operate in colder climates instead of the metal.
Also if you are going to be using it for combat use, i.e. for use with a handgun then the added shock absorbtion provided by the g2z will protect the p61 lamp assembly more than a z2 would from recoil. In my opinion the g2z is the better choice.
Mind you, you also need to consider whether you're a 'steel' person or not, my uncle bought a 6p instead of a polymer model because he 'just likes steel better. '
/ubbthreads/images/graemlins/icon3.gif /ubbthreads/images/graemlins/thumbsup.gif BTW I was going to get a z2 as well for this reason, but i've decided on the 6pn instead /ubbthreads/images/graemlins/wink.gif
By the way in terms of run time, i've had my g2z (running p61) for about six months and i'm still on the original batteries (although i think they're just at the stage where the light is beginning to dim). However I use my 8nx for general purpose lighting as well as my e1e and key lights. For the use that you have stated, 20 minutes is a looong run time for using any appropriate low light flashlight technique. Just keep your L4 handy as well as batteries and another p61 in a spares carrier and you're set!
You might want to check this out:
http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Board=UBB1&Number=362283&Forum=All_Forums&Words=g2z&Match=Entire%20Phrase&Searchpage=4&Limit=50&Old=allposts&Main=361317&Search=true#Post362283
My apologies if you have to copy and paste this link: i'm still a learning /ubbthreads/images/graemlins/smile.gif i'm off for some practice posting /ubbthreads/images/graemlins/grin.gif
Hope this helps,
Cam