I think the actual ride experience on a coaster changes with arms up vs arms down vs actually holding on. Check that, I should have said I know it changes the ride! In theory then, (and for me in actual practice), you get three different ride experiences on the same coaster, depending on what you do with your arms and hands.
For me arms up or down has to do with changing my body's center of gravity in the seat.
Also, arms up is easier to do after riding a coaster and/or "knowing" what it does.
I will ride Nitro later this month for the very first time, and my arms will be up from the get go, 'cause I "know" those B&Mers and I can already feel it!
*** This post was edited by MABrider on 8/2/2001. ***