(** My WM Summerlite plus a silk liner and a TG Raven bivy all stuffed into the WM XS sack weighs 31.5 oz. That is light! )
And both for me are quite true to their temp ratings. ( I can go down to 25 or a little less and be comfortable with a silk liner)
The Plasma is a bit more roomy. The WM SL is a bit on the narrow side. It works fine for me- but I am a side sleeper and that works a bit better. Can also open it up a bit and use it a bit like a quilt and also works quite well.
I received the Western Mountaineering 35 Degree Highlite, long, for Christmas. It weighs 17 oz. I bought a Sea to Summit Compression Sack which weighs 4.5 oz. So, 21.5 oz total. I haven't tried it out yet, but I have yet to hear anything negative about WM.
The Montbell U.L. SS DH long 30 degree bag is 1 lb 7 oz listed weight, been thinking about going with it and using a liner if needed.
I usually sleep hot anyway, and most of the time wear a layer at night anyway because I don't like the bag against my skin. Using the Big Agnes Encampment 15 degree long bag 3lbs 9oz, most of the summer and fall I was warm, out of over 35 nights in it last year I was cold and kept it fully zipped maybe 3-4 nights. That includes the 1st rifle season hunt I went on.
I have the mountain hardware plasma 32 degree down bag and I've used it down to 20 degrees with my base layers and I didn't get cold. It weighs in at 1 1/2 lbs. and it packs down to the size of a football. Love it