My Hewes 120 have the spring but I find it easier to ignore it as it seems difficult to attach the film straight. Hard to explain but positioning the film end in the centre and wrapping it on works fine. The pins for the perfs on the 35mm reels are great, by definition the perfs hold the film square.
What he said. Spring for 120, pins for perfs on 35mm. I use both, and unless I'm having a really bad day with the film, I always use the spring for 120 and it goes on great.
My favorite thing is to go where I've never been. D. Arbus