I would say that at normal boost pressures they are very similar in their output capabilities , where OFAB is better is when boost pressures get higher i.e. above 1.5 Bar as the std OFAC map sensor can only measure to this as a limit of boost and there is not an uprated item available , a std OFAB item can measure up to 1 Bar boost but can be swapped for either a 1.5 Bar boost (2.5 Bar total measure ) or a 2.0 Bar boost ( known as a 3 Bar map sensor as this is what it measures including vacuum ) .

I have just swapped my OFAC for OFAB not for performance but so I can get bits easier , the only issue with OFAB is the suppressor that ford decided to fit between map sensor and ecu , but a lot of people do not run these and do not seem to have any issues .

It is really down to personal choice and what you can get hold of .