Replying to Help sizing Armada Thalls Please!!!

I am looking at a pair of this years Thalls OR Ar7s. I would appreciate some help to get the right ski for me. Personally I was thinking the Thalls. For $30 more dollars I feel like it's worth it. I am debating between the 166 and 171.
LOCATION: I ski in Montana. Mainly at a small hill called Great Divide. A majority of the time I am in the park. I like to ski mountain a little too but I have JJ's for that. I ski about 60 days a year. Probably 55 out of the 60 are park.
HEIGHT//WEIGHT: I am 5'8" and I weigh 125 pounds. I am pretty much done growing.
ABILITY LEVEL: Type 3 park skier. Good all mountain skier too.
Thanks for any advice! +k for helpful and answers!