I'm sure Rolf will answer with his views - and they're always worth listening to - but I'd like to suggest a few....

The older boat can be expected to be less rigid (stiff), have some scuffs and scrapes, possibly be less watertight, have wear in the plate cases and rudder fittings etc.

All of these factors will impact on boatspeed - energy is 'lost' and not transferred into driving the boat forward efficiently. Of course ALL of these can also be addressed and the boat returned to 'good as new' condition and be on a par with, or better than, the newer boat.

Finally, the older boat may, if it has suffered from leaks or damage and repair, be heavier than the newer boat - assuming both were built to the same weight. This disadvantage cannot be readily dealt with and is something that any buyer of a used boat should be aware of when seeking out new (to them) ride.