The 2015 Blu-Ray is solid, probably the best one out there and it has both cuts on the disc.
I used to like the extended cut but over time I’ve come to prefer the pacing of the theatrical. One of these days I’d like to do a hybrid cut with just a couple of extended cut scenes restored…
(FYI I’m talking about the primary extended cut; the Easter Egg one has the cheesy alternate ending, I think.)
The second extended cut has the deleted scene in John’s bedroom, with the T-1000, and the Michael Jackson reference/Planet of the Apes make-up for Linda Hamilton alternate ending.
I don’t like the deleted scene where John Conner is trying to teach the Terminator how to smile - Schwarzenegger looks like a horse.