Well, they are all good boats really. The main decisive factor would be what you plan on using the boat for. If you're looking at playing at jumping waves, a hydro is obviously not a good choice as I'm sure you know. The xxx on the other hand would be a fun boat for that kind of stuff, plus it's a great racing mono too. For racing they are all good boats. The sport hydros will be faster than the mono if it's speed you're looking for.
I ran those tunnels for several years also before switching to gas. I ran 7.5cc K&Bs with the J tuned pipes. Had some HotShot Sprints, Prather 32" racing tunnel, and a few scratch builts, including an outboard rigger (that was interesting) and an outboard hydro built off of a design seen in Radio Control Boat Modeler a LONG time ago!!!
You will like the gas boats, I'm certain of it. If you have more questions, ask away and we will try our best to help you out.