Thanks for the question. I hope I'm not too long-winded, but I'm a huge fan of the Spyders and this is our second one. We rode the Dragon last summer on our 2008 RS and enjoyed touring around the Smokies so much that we upgraded to the Touring model. We're going back this summer.
I also have the Harley Road King that I like to ride solo. Both will fit in the toyhauler, but so far we've only taken the Spyder with us. Some friends just got a Harley Softail and we may haul it for them when the Spyder.
I haven't ridden a "two in the back" trike, but I understand they tend to dive in the curves. The Spyder runs the curves like it's on rails. It has a sprint car front end and while it doesn't lean, it does shift some. One thing some people don't like about the Spyder is that it does override things when it thinks you might be in trouble. If you go into a curve too hot and the computer senses front wheel lift, it feathers the ABS and drops the wheel back down. If you're still too hot, it can shut down a cylinder. I've only had that happen once.
I do have to remember when I switch from the Spyder to the Road King that I have to put my feet down!