does someone know what's the difference between the earlier Blood 1 edition "One unit whole blood" and the new "Fresh supply"? Anyone who has both and can say if buying "Fresh supply" is worth it (and why) when already having "one unit whole blood"?
The main difference is that OUWB runs on the Build engine where as Fresh Supply is on the Kex engine.
OUWB has been reverse engineered with BloodGDX and NBlood, both of which have their source code made open source. Unfortunately the act of reverse engineering is a grey area legally. NBlood is supposed to have been done as a "clean room design" project, which relies on independently recreating Blood's source code to run on the eDuke variant of the Build engine, so that may have a stronger position, legally.
The Kex engine is currently being supported by Nightdive Studios, however it is still proprietary. It is not Build, but it runs the necessary bits that make up Blood. They had to revers engineer Bloods source code and then get it to work with the Kex engine. Kinda like if you were to make U4E run the original Quake assets directly, without having to convert all the Quake bits to Unreal bits. B:FS is playable, and it's really fairly close, but unfortunately for the moment it is still a little buggy.
Right now, I would have to say NBlood supports Blood better than B:FS, but supporting Nightdive and Atari by buying Fresh Supply may
result in new Blood titles (if they can sort something out with Warner Brothers).
Hopefully that helps.