I think the SL is a little easier to live with backpacking. The cut is slightly longer and the pockets are much easier to live with if you ever plan on putting your handsin them. The pockets on the LT are a little awkward to access. The LT is heaevier by a very small amount and will be a little more weather resistant, but if you really need that extra protection you've probably got bigger problems. Either one would work great, but for backpacking I like the SL a little more than the LT.

---As Mike said, the Alpha LT is a tougher jacket due to face fabric and the backer material. As for freedom of movement, I'd say they are equivalent, but breathability is better with the Alpha LT. Also, the LT uses the Vislon watertight zip which is easier to use and more durable. It's my favorite lightweight jacket that Arc'teryx makes.

The paclite will be a little less weather resistant in harsh conditions but you will have slightley more freedom as far as movement goes while pursuing your activies. The pro-shell will add burleyness as far as wear and tear goes without that much of a weight penalty.In the long haul it will be a tougher jacket!

The paclite will be a little less weather resistant in harsh conditions but you will have slightley more freedom as far as movement goes while pursuing your activies. The pro-shell will add burleyness as far as wear and tear goes without that much of a weight penalty.In the long haul it will be a tougher jacket!