I'm a Storm/Roto guy at heart, even though I use stuff from all different manufacturers.
From the pictures I've seen of the Shift, it appears to be highly polished. Unless you've got revs out of your rear, I wouldn't recommend polished for medium-heavy to heavy as a general rule.
Judging from what you say your average is, if you are needing a ball for heavy volume, I'd go with the Pain. I've seen that ball in plenty of action from guys all over the rev spectrum and it is a arc-y, rolly ball with a ton of continuous action in the backends.
I wouldn't say 100 percent, though, until I see the Shift in use more than I already have.
Jess