In reply to Jonathan:
Got any links?
And which is 'best' depends on what you're using it for. Consider the quality of the down they use, and the overall amount, and the construction method - a well-made jacket with high quality down might be warmer than one that has a greater down weight but lesser quality. Also, if you're inclined, consider the source of the down and whether you're happy with how it's obtained.
Also, give serious thought to PHD's range - they're really good. For example:
http://www.phdesigns.co.uk/waferlite-down-jacket-k-series?osCsid=h21nau27o1...