Congrats on the Madone! I got to test-ride one a while back and it was fun.

Also, I love your description of the Bontrager saddle. I've never met one I liked.

If the Ariel saddle is comfortable after a long ride on the road bike, then stick with it. "Road" and "mountain" saddle designations are suggestions based on what tends to be comfortable for each type of riding (generally having to do with firmness), but they're not binding.