I'm assuming you are a member of the BAEC? If so, then BA miles are in my opinion far better than airmiles. The only thing is, to get them used you have to be a bit flexible- either in date or which destination. Through using AMEX for everything( and paying it off every month ) and doing all my shopping in Tesco( well- it is the only supermarket near to me anyway) I have had 4 sets of long haul flights now. I do have other ways of earning miles but these are the top two.
I won airmiles a few years ago and found them practically useless. The deals I found, I could beat anyway in my own research. However, others have been more successful I know.

Fiona - this is very interesting. I have thousands of airmiles and can't get to use them. Every time I travel I find I can do better by just shopping around. I earn most of these on my Lloyds TSB Amex credit card and via Tesco. How do you go about getting BA miles from Amex and Tesco?