Doom 2 version is mini episode with decorate things recommended to play through (That's not the normal map02 Underhalls). Doom 1 version I really felt the need to see all the vanilla format maps working in vanilla doom.exe and aligned some more of the original texturing better. Both have some different ZDoom maps and have something to offer that other doesn't, whether as secret maps in Doom 2 or additional episodes in Doom 1. ClassicT.wad is the best set of textures to use though