I purchased a neo angle shower and I am installing it on the second floor of my house. I have the pan down and I am ready to drywall. which is safer to use, cement board or green board behind the shower panels?
I would always use cement board in the shower area. I would extend the cement board to where you shower unit will cover. You can go past that point just plaster with a nice joint compound, like durabond to join to the rest of the plaster board for a permanent bond. I typically do not use green board unless you expect the wall can get wet, like a basement. My bathroom is upstairs and my house would wash away before those walls got wet, therefore regular board is fine.
In my upstairs bathroom that has a full 6 ft. whirlpool tub and shower I used cement board throughout the tub area for the long term durability before tiling. It has held up excellently. For the basement powder room, I am just putting in a stand up shower. This will not get as much use so I used green board on all of the interior walls of the bathroom and the tile in the shower area will be installed over the green board. This shower will be used less often and I did make sure to install a good fan to evacuate the moisture. If this shower was going to see regular use I would have installed the cement board in the shower area. My biggest concern is the interior of the green board. Although the paper covering is treated for moisture resistance as well as mold resistance, if your calking or other sealing products fail and water does find it's way into the center of the drywall, the drywall will wick up the moisture and swell. This swelling will further upset your tiles exasperating the problem. I don't think I need mention that this wicked up water is going to cause other issues that you will have to deal with as well. Which ever way you go I would make sure that your final calking is good and inspect it regularly. Chances are you will be sitting close by anyway from time to time, so having a quick look around is not a big deal. Good luck.