"greenboard" vs regular drywall
Regular board is fine (and cheaper) with proper paint. The greenboard of years ago had a core that was impregnated with (I'm guessing) some type of "oil based" product and it was much better than regular board for "wet" areas. The core of the board was actually a tan/brown color. I have hung many showers/tubs with it as tile backer. It often failed after time. Mainly because the hangers would set the board right down on the lip of the tub. Once the caulk around the tub failed (or even a leak around a faucet), water would "wick" into the board and it deteriorated. Everyone was under the opinion that this was "waterproof" drywall. It wasn't. That's why concrete type board is now used. The greenboard you get now has the same (white) core as regular board. Only the face paper is moisture "resistant". There are a lot of different opinions out there about this, but I haven't bought a piece of greenboard in at least 20 years. I have had a few customers in a commercial application request the "paperless" mold resistant type of board, but that's where they are expecting some type of water "intrusion" at some point.....
If you can read this, thank a teacher. If you can read this in English, thank a soldier. Support our troops.