More Information Requested:
May I ask, what is the motivation for a swap and who came up with the idea ?
Does either or both vehicles have a timing belt (as opposed to some cars that have timing chains) in the engine that controls engine function and keeps the engine from self-destructing until a maximum age / mileage is reached ?
Also, has this ever been replaced as regular maintenance (typically several hundred dollars) ? The information should be part of the cars’ maintenance schedule.
By the way, visible rust spreading on the body is often a sign that there is rust lurking in other unseen places and will sometimes develop into a safety concern. Have these cars both recently received a detailed check-up by a professional mechanic to see if anything needs repair ?
The better car is the one in better condition and the one that had a better maintenance history.