Originally Posted by
Daft Monk
You can put a free wheel on either side (which makes fixed/fixed better than fixed/free). In order to put a fixed cog on the free side, you'd have to do what people with conversions do and use a bb lockring.
Otherwise known as a suicide setup.
If you want the widest possible use out of a hub, then fixed/fixed is the way to go. You can put a freewheel on the fixed side no problems. Doesn't really work the other way around.