There are thousands of posts (really, no exaggeration) on dozens of websites about sleeping bags and the differences and advantages of synthetic v. down.
The basic rule is this-
Warm, Cheap, Light - pick two.

The more elaborate basics-
1. Down is warmer and compresses more than any synthetic for the weight;
2. Down costs more than a comparable synthetic bag;
3. Don't believe the temp rating unless it is an EN1357 rating or you recognize a top brand name (Feathered Friends, Western Mountaineering, Marmot, Mountain Hardwear, MacPac, etc.
4.Don't get fooled by an EN 1357 rating that isn't the comfort rating (you have to read up on this to understand how bags are rated);
5. Don't be taken in by "wonder bags" you see on eBay. Most of them are junk.

Snugpak bags are made in the UK. This link is to an American distributor-
http://www.snugpakusa.com/