Welcome to FT
getonplane
One question to consider is what are you looking to gain out of miles?
Are you more interested in earning status? In which case see BBomber's charts *A charts comparing programmes at
http://members.shaw.ca/deercroft/starall.html Or are you interested in collecting miles to redeem? In which case bmi have one way awards and cash and miles. Other factors to consider are actual routes/classes you might travel; any need for upgrade tools or household accounts etc.
Travel patterns and personal priorities will influence which FFP is best for you.