I think its no doubt about it the 36 inch kit will be easier to tip on its side. but I can't see it making a huge difference holding the side hill, I believe that is where the spindle comes in. I am going to try this 38 inch kit with the new spindle because I value some stability in certain situations and I don't mind being able to hold a sick side hill line either..
Other members have also spoke about the 36 inch kit paneling out a lot quicker.