Many differences in my opinion, motor comparing ISB to ISL, torque 800 vs 1250, 360 hp v 400 hp.
Chassis is huge difference, 5,300 lbs of GCWR, 47,700 vs 42,400. This is huge difference on equal size coach's.
Nothing wrong with either unit, just not comparing apples. There are significant differences between these two units in the guts. American has a very different factory support as well (at least that is my understanding).
To me the big question is how you will use the coach, your budget, and whether you can justify the real differences of the two compared to the costs differential.
I would also presume tire size is different, axles are definitely different. Good luck on your evaluation.