Sorry if its been asked before, but I'm planning a 2013 thru hike of the PCT. I'm debating which bag to get. I've narrowed it down to either a Feathered Friends Swallow with 3oz of overfill, or the Western Mountaineering Alpinlight. I am 6'0" tall and weigh about 185. Thanks

Obviously there is not all that much difference between the two. I think you could flip a coin and be happy with either. Does one come in a colour which you prefer? ;)

The Swallow would be slightly (4") narrower at the shoulders, which may or may not suit you (warmer, too constricting). With the 3oz of overfill in the Swallow you should have a similar warmth bag. The Alpinlite does have the permanent collar though which would help keep the warmth in. Personally I prefer the button style closure on the hood of the Feathered Friends bag, but that is preference.

The real deciding factor would be Nanosphere vs Extremelite vs Pertex Endurance UL.
I will let you do that research for yourself as there is a lot of marketing spiel involved that I do not feel entirely qualified to cut through.

Sounds good. I'll call Feathered Friends tomorrow and see what I can get. With the bags being so similar, I think I'll go for "smaller" cottage brand. Thanks for the input.

The FF swift compares to the WM Alpinlite while the FF Swallow is comparable to the WM Ultralite. You'll see their dimensions and their fill powers are much more similar.

As for which style to go with, it pretty much is a coin flip. You'll be happy either way. WM has the benefit of being more widely distributed (you can buy from BC.com with their great return policy). FF has more customization options, and the nanosphere fabric is probably one of the most water resistant fabrics on the market currently.

So flip a coin on manufacturer. As for which model, depends on how claustrophobic you can sleep. If you don't mind a tight fit, get the narrower Ultralite/Swallow because it is more thermally efficient. If you want to push your 20F bag colder by wearing down clothing to bed then maybe go with the wider bags that won't compress your extra insulation as much.

I have the WM ultralite and love it. I'm 5'11" and 160 and it's plenty wide for me even with a thicker puffy layer on (or rather going slightly wider doesn't really give me enough moving space to make a difference). Since you're a bit bigger the narrow cuts may not optimal for when you want to push the bag colder (but not impossible to do either).

Here's a link to the specs for both WM and FF. The FF has measurements listed under the name of each model.
http://www.featheredfriends.com/Picasso/Subhead/BagCharts.html
http://www.westernmountaineering.com/index.cfm?section=products&page=Sleeping%20Bags&ContentId=27

And here's prices (MSRP) for WM
http://www.westernmountaineering.com/index.cfm?section=pricing

I haven't hiked the PCT, but do a lot of backpacking year round in Oregon and Washington. Once upon a time I had a WM Alpinlite, it was way too warm for Spring/Summer backpacking in the PacNW. I don't want to say don't get it, but perhaps the Megalite or Caribou should be considered as well. The Alpinlite, while really warm and 2lbs., was pretty bulky in my pack (compared now to a Katabatic Gear quilt). If you plan to sleep in all your warm clothes, as most thru-hikers do, I think a less warm/less bulky bag would be the way to go, unless of course you tend to sleep cold.

Yes, Dustin is correct wrt the comparison. The Swift is the wide bag. I have one with 2oz of overfill and went with it over the WM because it is functionally wider everwhere and has a more durable exterior fabri (at the expense of some weight).

Is it too warm for spring and fall? Not where I trek (the Canadian Rockies) where it will jet past freezing in the summer.

I am extremely pleased with the design of the bag and it is heavenly warm. The full zip allows you to vent effectively and the differential cut of the hood is the best I have ever used.

A bit of a toss up between the two bags, however.

You guys really got me thinking, but in the end I decided to go with my first choice. If the bag were just for the PCT I'd probably go for a lighter 30deg bag, but since I also spend a good amount of time in the Sierras in late Fall, I went with the warmer 20 degree. I just ended up purchasing the Feathered Friends Swallow with the Pertex UL fabric with 2oz of overfill and decided to get funky and go with the tangerine color. Thanks for all the input, it definitely got me thinking.