I tried a +4 Demo Car and a recent Pre - Owned 4/4 before opting for another 4/4. Roadster was luckily not available; Madame had already vetoed one on cost... There appeared to be very little between the two cars to me. Admittedly, the 4/4 was Run - In, whilst the +4 was still fairly new.
There was more Mid Range Punch on the +4, but certainly nothing that made you feel that it was a 'performance' car compared to the 4/4. I came away feeling the +4 was a bit of a Con.
A 'Con' that seems to be drawing in the Punters as 4/4 production has dropped from 3 to 2 a week.