Honestly, I find Orion to be pretty overrated. I love Call of Ktulu and To Live Is To Die, and both Suicide and Redemption and Pulling Teeth are about as good as Orion, but the difference between those two and Orion is that they don't get anywhere as close to the amount of praise it gets. I respect that it's used as a tribute to Cliff, but I feel Cliff delivered far more in other songs with the band, and had Cliff not tragically passed away during the Damage Inc tour, I reckon it would be nowhere near as revered.
77 took a while to get going with an average build-up, but the atmospheric parts in the middle are great as well as the conclusion.
78 is most famous with its inclusion in the Exorcist, and the atmosphere and ethos it creates is still evident to this very day. It's a chilling track used to create tension and it fulfils its role perfectly.
79 sounds like something off a Sega Megadrive side-scrolling beat-em-up. I like it. It's a swanky song that's a lot of fun to listen to and doesn't take itself as seriously as the others in its heat. That's something I respect.
80 was discussed above, but with all that said, it's still a good song by Metallica, just nowhere near as good as two of their other instrumentals. I don't find it as atmospheric as their other instrumentals though, as it seems they're going through the motions with the track here, as opposed to focusing on a specific emotion (With Ktulu, it's chaos, with TLITD it's sorrow).
I feel bad for 77 for getting such a nasty draw but the application of 78 alone makes it the superior song due to its atmospheric use and impact in film.
At the end of the day, 80 is a good Metallica track, but far from their best instrumental work. 79 on the other hand set itself a target to be simply a fun, enjoyable song to get into, and they nailed it for me.
78 and 79 for me.