What I liked most about Devil was that you flew around the mine very much like you would in the game itself. The navigation controls are just like flying the Pyro. DMB2/DLE-XP take more of a God's-eye-view approach where you're often seeing things from a distance. I always found it hard to make dense levels with DLE-XP. The view warping is pretty drastic and there are a few clipping issues with polys appearing in front of other polys (probably a z-buffering issue somewhere). The other thing DMB2 always did I found awkward was how it decoupled rotation from scale. If you were zoomed in on something and then rotated the view, the whole level would swing around based on some axis faraway instead of always basing the rotation axis on the camera position.
Devil also had a vastly superior curve generator for a time, although Descent Blocker Builder II was a big boost for DMB2. DMB2, however, was always better at cut/paste/import operations. DMB2 also let you see the mine with textures. Although Devil sortof let you do this, I don't think it's possible to see the whole mine textured... just the immediate cubes.
Though, given that I've forgotten most of Devil, it'd probably be more alien for me today than DLE-XP is.
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But I'm happy to try this.
EDIT: Ooh, this brings back memories and I got used to the controls really quickly.
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Too bad it only seems to run in 640x480 (higher resolutions crash) and you can't work with Windows (Devil dominates the taskbar). Hmm, it's a really great springboard though!