I just received my new bag that I picked up for 25% off at BackcountryGear. Montbell UL Spiral Down #3 in Long. I'm debating between this and the WM Summerlite, which I have looked at in a store, but do not have here to side by side compare. The MB bag is very appealing as it has a significantly lower price (even w/o the 25% discount) to the Summerlite for almost identical specs:
The Summerlite is rated at 32*, the MB at 30*, but I doubt one could tell the difference in the field.
The Summerlite weighs 19oz in the Regular, which is the size I'd take. The MB also weight 19oz in regular, but I have to use a long, b/c the 5'10" length of the Regular is a hair to short. My long is spec'd at 20 oz by MB. On my non-digital postal scale, it comes in at 20.5 oz, so pretty close.
After letting it loft for 45 minutes, I used a tape measure and got ~3" of loft. Some spots were close to 3.5", but overal I'd say 3" WM claims 4" for the Summerlite. Some picturess:
Next to my REI 1.75" trekker.
In Stuff Sack
Holding it up to the light, the light fabric showed through spots where the down was thin on it was just fabric against fabric. I assume with a bag this light, with 10oz fill, this is just the case. I tried it with the summerlite in the store, but the inner lining is black, so I didn't see any light through it.
The MB bag has a draft tube, but it is not down filled. The Summerlite has an 'insulated draft tube' which I assume means down.
Neither has a collar. The #3 has a draw string at the neck that pulls pretty tight.
The big negative about the #3 to me, which I did not notice looking at the photos, is that the zip stops 2' from the bottom of the bag. I prefer a full-zip so I can use the bag as a quilt in warmer temps. I also like to be able to vent my feet. The summerlite is a full zip.
I'd be happy to (attempt to) take any more detailed pictures anyone wants.
Of course, the main measure of the bag - will it perform - I can only find out by taking it out in the field and rendering the bag unreturnable. I may have to order a summerlite to put them side by side.