I've ridden the T-hall for 2 years now, and I've been SOOO satisfied. I've tried a couple of other skis (4FRNT's, Dynastars, Rossignols etc.) The only skis that can compare with the T-halls are Rossignol Scratchs, but I'd say the T-halls are still a better choice.
The biggest (only?) difference between AR6 and T-hall are the flex. The T-hall are softer and more playful, while the AR6 is a better all-mountain ski and would probably be a better choice if you're doing a lot of giant jumps. But the T-hall will not be a problem there either (if you're not superheavy).
Atomic makes great racing-skis, but I don't know how their park-skis are. They're probably plenty durable, but I like the core companys a lot better when we're talking twintips.