I have used Rio's, Maxijets, via aqua's, Seio's and Koralia.
I like Seio and Koralia the best.
When you put the fish guard on the Seio it is completely safe. The new Koralia's come with a fish guard that goes over the out put that makes them safe for seahorses. The guard was not originally included but has been for awhile.
IME jet stream style pumps like the maxi jets are the worst choice. The flow from a maxijet is very narrow and pointed and even though it's half the flow of say a Seio 620 the reaction of a seahorse swimming in front of the two is much more violent with the maxijet.
IMO the jet stream or fire hose style pumps are not the best for our aquariums. We want the flow to be wider and gentler, better for the seahorses better for the corals.
Maxijets are incredible pumps for other things. They work great to power equipment, you can use them for a return, a little mod you get a very strong and wide flow power head that consumes very little energy. I just don't like them in my systems.
I spent a long time playing with flow, trying different things, my seahorse tank turns over 47x an hour. It took some doing, but it's nice.