Well, concerning my business flights (mostly within europe) in most cases I am not really able to choose myself, but if I could, the following factors would be important:

1.) Simply the costs (if I had to pay myself ;-))
2.) Best connection, direct flights, or just a short stopover (but not too short, I hate hurrying from gate to gate)
3.) Loyalty program

Everything else - like service, meals on board, aircraft - is just a nice "extra" for me, but it would not really have influence on my decision.