funny because theres a ton of people on this website that swear by the t-hall...skis are totally objective and I daresay whoever has the ar7s is just a better skier than the guys with the t-halls.
To the OP:
The AR7s are more all-mountain oriented, and not very buttery, while the t-halls are park oriented and a good mix of buttery but still stable on jumps. If you're going to be spending >50% of time in the park definitely go T-halls, especially if you're lighter, and even if you're spending less than that amount still consider them. The AR7s will be less buttery but will perform a bit better all mountain wise. If I was in your situation I'd pick t-halls, but you can't go wrong either way really, they're both solid skis and have their merits.