Just by glancing on their website, Aero seems to be more expensive than PSA. If I get near the $1000 mark, then I have a couple of complete pistols that I'd consider getting instead of building one.
My decision to buy Aero Precision over PSA is based on two things it particular.
First and foremost, White Oak Armaments, who caters to serious High Power rifle competitors, uses and endorses AP.
Secondly, they (AP) offer their receiver sets in various Cerakote finishes that I like, particularly OD green.