Matt
The Amanwana's dive center, when I was there a few years ago, had about 3-4 sites I hit for the week. I don't have my notes with me but I remember they were many high current sites with half decent pelagic action like grey reefs and nappy wrasse. The coral is nice is some areas but there's also fish bombing still (even if it is a national park). Mostly the sites are better for video, stills would be difficult in the current as you'd just be flying pass everything. I do remember the viz was awesome the few times I'd been there at the resort but my liveaboard itinerary always bypasses Moyo for Sangeang and Satonda. Of course it's all subjective since I think many places aren't great in Indo and others rave about them.
Seraya's immediate area is the wreck, dropoff and muck diving. Nothing much in terms of pelagics but you get the odd Mola on the wreck and in the cleaning stations deep in Seraya Secret. Seraya secret is a great muck site for crustaceans. The wreck has the great 'cuda, the school of trevally and other nice stuff. It's a really nice wreck dive. If you've never been, I recommend it. Diving from the boat is the best way to do it IMHO.
Sumbawa isn't that far from Bali so it shouldn't take you the entire day to get to Seraya. It's 2.5 hrs from DPS. You should be able to get a night dive or 2 in. You do lose a day of diving in Moyo unless you take the seaplane from Moyo straight to Seraya.
