the artists I have talked to about the difference between rotary & coil,is that most say they can tell how the ink is going in better with the noise of a coil, :) that makes sense to me.
I've been tattooed by both,and I don't feel any difference,if anything like was said,the coils sound more aggressive,so it's probably a mental thing.
also,when I walk into a shop and they are using rotary machines,it just seems like something is wrong,or missing LOL , I know it's the way things are going,I'm just sayin.
and as far as the pain ? yes,it's a mind thing for me,I sat for an 8 hour "one shot" yesterday,and I can close my eyes and put myself somewhere pleasant,it's about extreme concentration on something else that helps me.but I agree,it still hurts either way,no matter where you get it,just different degrees of pain,it's up to us how we deal with it,I believe in the mind over matter thing,it can work.It got me through last night anyway.
IMO the worst pain is the shading & highlights that hurt the most,the going over already tattooed areas that hurts the most.