I have a set of SOTAR cat tubes I bought new in 2006. I've been down dozens of rivers with them, I've dragged them over rocks, abused them, and have had no problems, no patches, no leaks, they hold air extremely well -- they're still going strong. So when I bought my round boat this year, I went SOTAR again, because I trust my past experience. They're great boats.
I went with the ST, primarily because of cost considerations, but I'm very happy with the boat. It tracks and maneuvers well, and hauls a boatload (heh) of stuff.
I hear really great things about Maravia, too, but I have no direct experience with them.
The designs are a little different, so you may want to check out which suit your needs better. I honestly don't think you can go wrong either way.