The Arc'teryx Alpha LT has a lot of buzz for a couple reasons. The fit and finish on Arc'teryx is unmatched. Super tiny seams, no external stitching, and no rough edges on the seam tape make for excellent fit and great durability in a lightweight jacket. Also, the face fabric is of higher grade than any other coat; it uses tiny threads, that are tightly woven for a smooth hand but high abrasion resistance, this also helps hold the DWR finish much longer. The similarities on paper will quickly fade when you pull on the Alpha LT.

for the Arc'teryx Alpha LT hood, the pros of the storm hood (no separate collar) better coverage on your face, especially when the hood is up. It really seals up, and you can tuck in really deep when the wind and snow are howling. if you wear it in milder weather, the front part doesn't lay as flat as a collared version. The Arc'teryx Beta LT is the alternate version of this jacket with a collar and roll-hood,if you prefer that style.

The rumor you've heard may be a reference to some of the snowsports pieces Arc'teryx makes (called Whiteline). The Ascent collection (climbing inspired, such as this jacket) maintain the trim fit, but still allow for plenty of layers underneath. Go with your standard size.

I just tried mine on with some layering underneath. I'm 6'3", 185lbs, and I can fit a Patagonia R2 fleece and a Patagonia Micropuff vest underneath comfortably, still allowing plenty of movement.

i second Mike's opinion. I'm 6' 4" 185 and the large is dialed.

Go with a large!

I can vouch for the Alpha LT. The difference is in the face fabric, not the backer (both have woven Pro-shell backer) I've been wearing an Alpha LT for a couple years, and it's my favorite shell, ever! It's face fabric is way more durable than you'd expect for such lightweight; I've never babied mine (quite the opposite, in fact) that being said, the Theta AR will hold up just a little bit better against abrasion, but it's definitely bigger when it's in the pack. For ultimate toughness, Alpha SV.

I can't vouch for the Alpha LT, but I have the theta ar and have put it through hell. I have been through thick woods, slid down rock embankments, and scrambled through thorn bushes (not a snag). It has been crammed in my backpack numerous times, stored in the floorboard of my truck, and used in all temperatures and it looks like new. It has been the most durable shell I have ever owned (although I recently got a sidewinder sv and have yet to put it through the paces). You can't go wrong with any arcteryx shell.