Man, you guys are really getting into this discussion, huh?
It's pretty obvious that procedurally generated (PG) and hand-crafted (HC) both have very good things going for them.
PG gives the game near infinite replayability if you really like exploring, but the game world would kinda end up being a bit boring and not very memorable or special in any way.
HC can be very well designed and memorable and special and all that awesomeness, but it may tend towards things being a bit samey, where you end up knowing all the locations of things you're looking for and every time you decide to play through the game again you end up going through the same thing to get the best things for whatever playstyle you've decided to go for, and whatnot.
There's also the whole speed-running thing, which, to be honest, I don't think would work very well for Sui Generis. Most speedruns are either based on either using very high skill to do things quickly and efficiently, or exploiting bugs and glitches to skip parts of the game. The skill thing won't really work for a game like this, as that's more applicable to a platform game or something like that, and exploiting unintended glitches would likely not work very well, as Bare Mettle would notice and probably end up fixing the glitch if it's a major one.
But, people still love to speedrun things, so PG isn't really going to work for speedrunning (and who are we to deny them the opportunity to do so?), so it's got that against it too.
Really, I kinda tend towards PG because I like exploring, bit it's probably best to go with HC, to be honest. Any ideas we could come up with that combine PG and HC with HC bits floating statically in a PG environment would probably not work very well, or just defeat the purpose of having the game be HC or PG.
Plus, it would take up some valuable development time implementing any PG environments, and Bare Mettle weren't planning on having PG environments, so it would kinda mess up plans a little bit, no?
We could probably just hope for the best and see if someone makes a cool mod that generates a land-mass and a dungeon, or maybe ask Bare Mettle nicely, once the game comes out, if they could consider adding in some PG dungeon with an entrance in some small corner of the world, or releasing the map-making tools so we can work on said mods...
So yeah, having Sui Generis be HC initially, then seeing if either BM can add some small PG segment as an extra after release, or someone can make a mod, or for some other way to have a PG world be an optional possibility for those who want it would be the best thing to do, really. It would (hopefully) please people who like HC worlds and PG worlds as well, since you would end up having an option for one or the other.