I have to say I agree 100%. I love my S3 and will probably have it a while since phones cost a lot off contract but I too love my Nexus 7 for its flexibility and control. I just put AOKP on my S3 and a new kernel and I love it, but its still not the same as a Nexus. I don't regret passing up the Galaxy Nexus because though it is a Nexus, it just wasn't quite there for me. To me, CM10, AOKP aren't AOSP. They are good but aren't pure Google. They have additions that are good, but I really like my Nexus 7 and its pureness. At times I feel the customizations of CM10 AOKP and the rest get in the way sometimes.
Not to mention we'll (and the N7) will already be on Lemon Drop when the S3 folks will still be talking about a possible KLP leak.