Have to say the monitored approach thing shouldn’t be a factor in your decision. Moving from a different airline to BA I wasn’t sure at first. But after a few weeks I actually prefer the monitored approach as gives you something to do
each sector.
In terms of your decision - if you are happy doing the same type of flying on the same routes for the next 30+ years then that’s your decision made. Personally I would get bored and the option to have a change every 5/6 years is a major benefit at BA