dtgreene: Differences between the Steam and GOG versions of Arena and Daggerfall, from what I've read:
* Arena: The Steam version is the version released on floppy disks (I believe it's the final floppy version). The GOG version is the CD-ROM version, which has voices that weren't in the floppy version. (I think it might have a potentially game-breaking bug that's triggered by collecting the same main quest item more than once, so don't do that unless you're doing a glitched speedrun.)
* Daggerfall: The Steam version is the original 1.0 release. The GOG version is patched to the 2.13 release; note that it's missing some of the bugs present in 1.0. (Worth noting that Daggerfall is notoriously buggy.)
slickrcbd: Might it be worth getting even if I got the version that they had on their website years ago? I'm not sure what version that was. I installed it on my old computer and don't feel like booting it to find out. Win10 didn't even exist when I downloaded them.
BTW, what's the easiest way to identify which version?
I don't know if there's a way to check the version directly, but you can check something that differs between versions.
Arena: Start a new game, and listen to the dialog at the start. If you hear speech during the cutscene, you're playing the CD-ROM version; if not, you're playing the floppy version.
Daggerfall: Start a new game, then once you gain control, press F11. On a fully patched version, this will warp you to the dungeon exit (this does allow you to skip the tutorial); on 1.0 this will do nothing. (This feature was added because of complaints about players falling out of bounds and not being able to get back in bounds.)
The versions they had on their website are the ones apparently found on steam, except that the version of Daggerfall came with the patch, except that the patch was not installed by default; instead, you had to run a separate executable included with the game..