Yikes! Amazing amount of information. Thanks!
My wife and I have been to Galapagos twice (going again this coming April - I hope the hammers will be there!!), Malpelo once, Cocos twice, and Socorro three times. They are all different and all pretty amazing IMO. Socorro is the most "beginner friendly", but even that can be challenging, especially at Roco Partida so I'd certainly recommend a minimum of 50-100 dives before going there. The other destinations can be even more challenging. Here's a very quick summary:
Galapagos November - We "only" saw two whale sharks, but every dive was fantastic. There was a tornado of activity on almost every dive, with various sharks, turtles, sea lions, tuna, tropical fish, etc, It just never seemed to end. On one dive, I was drifting in the blue off of Darwin when a school of tuna came in and darkened the sky. I was in the middle of them as they whizzed by, and all I could see top to bottom and 360 degrees was tuna. Also, experienced wicked current - on one dive we were all blown into the blue and surfaced more than a mile away. We also experienced the roughest seas ever in more than 30 liveaboards throughout the world.
Galapagos August - Saw 11 whale sharks! Saw mola mola, saw everything above including tuna, but in a school not quite as large.
Malpelo July - Middle of nowhere! If you get into trouble, you are SOL. NOT for beginners. You are at the mercy of the boat crew so book with a proven outfit. We saw whale sharks every day, hammerheads, eagle rays in formation, massive schools of jacks and creole fish. And schools of silkies - the only place where we have seen schools that large - hundreds of them
Socorro - February twice and March once. First time we went, the Solmar V was the only boat there. Second time, there were more boats, the third time (March 2019), there were 6 boats at Roco Partida! We still had great diving, but I'm afraid the place is going to be destroyed if they don't limit the boats. We had 45 minute limits on dives and we'd jump in just as the prior group was leaving so there are divers on the same site constantly for 8 hours each day! It's not what is used to be, but the manta and dolphin encounters are like nowhere else. We saw sharks too, but not anything like we've seen elsewhere. Socorro is for Manta and dolphins. You can see whale sharks, humpbacks, bait balls, and big schools of hammers, but those are hit or miss. I really hope this amazing place doesn't get destroyed, but even more boats are heading there!
Cocos - May and October. I can't really say that the conditions or life were different based on our two times there (and the trips were 10 years apart). The last time we went was in 2010. The tigers were there unlike the first time. The water was rough to the point were more then half the boat was sea sick and didn't do much diving. My wife and I did every dive and didn't think it was that rough. Diving was great both trips, but we saw many more hammer heads on our first trip. We saw one whale shark on the 2nd trip but none on the first. The night dives are just crazy, but I don't think they are doing them anymore, and frankly, I don't think I would do them again given the tiger issues they have had.
BTW, the whale shark in my avatar wasn't from any of the above trips. I shot that in the Sea of Cortez.