Most excellent question Blast. I've used the fleece blanket many times as I don't have a ponco liner. I've got a fleece sleeping bag big enough for a 6'1'' 240 lb guy crammed into a stuff sack small than a loaf of bread. Yep, it weighs a little, but not much.

As for the spark issue, I know that I have a fleece jacket that I was wearing on one outing and after being around the fire all night, I had several small holes where sparks had caught and actually burned right through. I would imagine the blanket would act the same.

I would interested to see the difference between the two item while wet.

Coleman makes, or rather made a 32 degeree bag called the Canyon that really scrunches down. It's only a 32 degree bag with clothing...trust me, but it works great for early fall trips. I got mine on eBay for really cheap.
_________________________
Get busy living...or get busy dying!