I can't compare to SPS corals, because I've never kept them, but to compare with some things I have specifically kept, i.e. agressive fish (puffers, filefish, triggers and lions) and octopus, and regular reef tanks, they are much more difficult, require more constant observation, and have far different nutritional needs with their own specific problems.
The biggest problem is getting pipefish and seahorses to eat. Just because you offer it, no matter what it is, doesn't mean they are going to eat it. If they don't eat within 3 days, there is a very good liklihood that their digestive system will shut down, and they couldn't process food even if they did eat it.
Setting up their tank is usually in the normal params for most SW keepers, but so many things can make them stop eating, and nearly all are stress related. You, as a seahorse keeper, have approx 2 days to recognize this and correct the problem before it leads to your fishes death.