From what I can see the radius of gyrations are the biggest difference. The Attitude using the Shape Block core & the Spec. Agent using the EMC Core. The SA looks like it has more of an arcing hook & the Attitude more of a sharp hook. But a lot has to do with the way you have them drilled & how you release them.
I have The Special Agent & the regular Shift. I do see a little difference in their break to the pocket. My Shift is Pearl particle R2s &w/it's core never loses energy even off light oil to dry boards & actually snaps more off that friction, where as the Special Agent, if I over rev it will lose energy. It also seems like if I do over rev the Shift, the worst that happens is that it goes brooklyn, but usually w/great carry. Now I'm sounding like I'm reviewing the regular Shift, sorry, wasn't my intention.
I would check Storm's website & reviews of both balls also.
I am seriously looking at the Attitude Shift for myself also. Mainly because I am a fan of the Core & love my Regular Shift so much if you couldn't already tell.
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Just grip it & rip it!