Can just imagine the line at Waddo or wherever with the crews fighting for the 737-800 over the old Britannia 737-300...."you had the 800 last time, that's not fair"!
An ancient Air Eng on 33 used to tell of his time on post-war Lancs- "We'd drive along the line before a trip, and say, 'That one!' It would be the one with the least oil all over it."
There was a choice in them days, evidently.
CG