Should I sear meat which is cooked sous vide before it goes in the bag, or after? After reading the beer cooler sous vide hack, I'm tempted to try it probably with duck, but maybe with steak.  

Should I sear my duck/steak first before I put it in the bag, or afterwards, and why?  Or does it not make a difference?
After a bit of googling, I found this which suggests that searing twice (both before and after) might be preferable.