neither they arent pow skis.
how old are you?
if you are still growing then the ar7 might be best for you, the thall can get slightly sketch if you dont land perfect at 45 ft.
plus when you get older your balls will get bigger and brain smaller and you will try bigger jumps and thusly the ar7 would be better. but if you can get new skis every year the thall is best for this year. or if you are done growing