I'm gonna be ordering the Spiral Anthems when I get home in a few hours and am stuck on size. I'm 5'8" and weigh 140ish. 171's or 178's? I'm only gonna be skiing them in the park.
Go 178, you'll be happy with it. They will be more usable all mountain while still slaying park. Small skis don't have the same "feel" as big skis: I'm 6'0, 185, and I went from using 171 Salomon 1080s as my everything ski to 185 Scratch BCs, and I love them. Its a good feel.
I would say go for the 178's because the anthems are a pretty soft ski. If you're ever stuck between sizes its always safe to go longer. Plus they'll be more stable if you do some all mountain stuff