Hi, what are the differences between the two versions?

original D3 - skippable cutscenes, barrel boost, slower movement without stamina, archvile jump, long loading times, 60fps lock. BFG - unskippable cutscenes, no barrel boost, faster movement without stamina, no archvile jump, fast loading times, 120fps.

Someone correct me if something is wrong/not true.

so the original D3 is faster?

Well, you can use source-port for BFG edition, which has skippable cutscenes, thus it's faster. The question is if you want to use an unofficial version for speedrunning.

By how much BFG edition is faster than the original when using the source-port?

That's hard to say since the current original D3 run is really outdated. I guess maybe couple minutes?

I see, thanks for clarifying!

I'd assume probably around 5 minutes or so depending on hardware. Hard to say, really. BFG also has more ammo and such that make the game a tad easier, as well as the flashlight mount.