We were thinking about getting both for our son. His Birthday is coming up.
About how small do these stuff down to for the pack?
Compared to their down equivalents not very. I put both into a compression sack for my last outing and had trouble getting the compression sack in and out of my ULA Circuit. If you keep them in their original stuff sacks they'll fit in the pack, just don't expect to pack much around them, on top of yes, around not much room. But remember I'm using ULA Circuit with a 2400 cubic inch mail body, so there may not me an issue with a larger pack. For instance my 60 liter pack has far more room.