I actually JUST finished testing both... at a very high cost. I ran the aim heavy build with a 7/3/31 and aim augments and then tried the 2/8/31 build with power augments...
Go power. drop crit chance and stack power. I think my crit rating is at 159 or so... considering most of your damage is yellow (tech) and only rapid shots and rail shot are white (ranged) you can afford to drop crit since you get perks from buffs and spec for increased crit chance on rail shot and your tech crit chance will still be at around 30% which is where most of your damage comes from anyways.
I know many will say aim but after testing myself... me and all the other PT's in my guild who have all tested it at some point all ended up with the power build. I noticed a nice increase in over all damage. Some even drop crit rating more but I prefer mine at the 159 rating it's at now.
Damn the cost, but why didn't you test 2/8/31 with power augments? And then test it again with one less crit mod/enhancement and one more power mod/enhancement?
I mean 2/8/31 may just be that much better of a spec.