There are other differences JAA v. FAA that are significant for many people.
The CAA Class 1 audiogram (and indeed much of the CAA Class 1 medical) has a demonstrated ability option which you can invoke on any renewal.
You then get e.g. unlimited uncorrected vision, and unlimited hearing loss, and you can fly commercial as an ATPL on that.
The problem for many is that the JAA initial medical has no demonstrated ability route, whereas e.g. the FAA medical does. It does not make sense to have an initial medical different to a renewal medical, if you think about it.
On the colour vision for example, the FAA allows you to take the demo ability as far as recognising standard tower lights, which is not a problem for the vast majority of pilots who can see all the normal colours one sees in normal life, but would otherwise fail the Isihara and even the Lantern Test.
To answer an earlier question, there is little point in somebody working to be an airline pilot to do the IMCR unless they intend to fly privately also. The whole drift of airline pilot training nowadays is to go away from the traditional "self improver" route to a quick integrated course, mostly in a simulator, and then straight into the RH seat. The airline pilot needs to not have a clue about GA flying.