BD hands down - fast earning on paid business and first classes, and GREAT for burning - it's the ONLY Star program that allows one-way redemption for exactly 1/2 of the miles required for roundtrip. Plus they have Cash and Miles, also unique in the Star universe.

Diamond Club is getting VERY generous, thanks to bmi's possible acquisition by Lufthansa. Go to BD thread for more details. I can't find another program gives you 2500 miles for answering 6-question surveys done in a munite!