I myself have the US UltraHD set, which also carries the Blu-ray. I will note on all blu-rays of the first film are the same with over-DNRed picture. (DNR =
Digital
Noise
Reduction aka grain removal.) The first release contained a dated MPEG-2 transfer. So the UltraHD is the way to go in both resolution and picture quality. As it restores the film grain. As for extras the last 4-movie set should carry all the that were on the DVDs unless otherwise. Use
Comparison Search: Predator, for further info on extras.
This should give you an idea of picture quality for the first 3 films:
https://caps-a-holic.com/index.php?s=PredatorAnd welcome to the forum Alan Schaeffer!