UK ICON 4K Blu-ray

UK ICON 4K Blu-ray (caps)

UK 4K Blu-ray has a slightly better encode than US Shout! Factory 4K Blu-ray and Germany StudioCanal 4K Blu-ray

5.1 mix is flawed on Shout! Factory/ICON, a phasey upmix instead of the proper discrete surround. The UHD 2.0 tracks are downmixes of that track.
2008 Fox Blu-ray sounds great, very close to the original 70mm mix, only with split surround.
2001 DVD has the original mix as 4.1 and matrixed 2.0.

Imprint 4K has a 4.0 track. The StudioCanal 4K Blu-ray has a different 5.1, unclear if it's the same as Fox BD.

2015 Lionsgate Blu-ray 

• 2015 Lionsgate Blu-ray (but it's missing the extra scenes in the Ultimate Edition)

• 2017 StudioCanal 4K Blu-ray and subsequent 4K Blu-rays are notorius for being heavily denoised and smoothened. Alternatively, 35mm scans for the theatrical cut is also available.

• For the Ultimate Edition with the T-1000 searching John's room and the happy future ending, the 2009 Skynet Blu-ray, which is the older pre-2017 transfer, but has DNR.

• Original Kodak/ORC CDS mix:  Japan Pioneer DVD in DTS/ac3 5.1

• Original Dolby Stereo SR: USA Widescreen LaserDisc and others.

differences of mixes on various releases: see thread and more info here.

2017 Blu-ray (which has the DNRed transfer), the 2009 Skynet Edition Blu-ray, and the 2000 Ultimate Edition DVD have exclusive extras. The 2003 Extreme Edition DVD has some exclusive easter eggs.