Arc'teryx Alpha IS vs Arc'teryx Beta LT

It has increased bulk and hence a natural clumsiness to its form versus the closer-fitting agility or sleeker esthetic of its predecessor.

I’m a size 36 waist, which sometimes suggests a size L, and I sometimes find myself between Arc sizes with broader cut pieces like the Fission SV or LEAF Cold WX LT fitting me better in a L. Certain fleeces like the Delta LT and Kyanite LT also fit me best in a L, so I had some concerns the Acto FL might be a bit too baggy, but it is a very trim cut piece and ultimately fits exactly how I wanted it to.

This jacket is excellent for its weight and thickness. It's not puffy nor thick with down, but it performs well above many of my heavier jackets. It's very comfortable, and not at all restrictive. It definitely feels like it's made to be worn over another jacket or some other insulation

However, if you care about every ounce and packability, go for something with down. I like the Uniqlo packable down hoody. It's a few ounces lighter than the Arc'teryx and packs down smaller.