Which John Deere 345?

Looking at two 345s.

First, a 1996 18 hp 48" with 668 hrs. for $2700.

Second, 2001 20 hp 54" with 471 hrs for $3200.

Both are one owner in similar condition. I am leaning towards the 2001 for the lower hours. Have seen a comment that there might have been some problems with the 18 hp in the earlier 345s that caused them to go to the 20 hp in the latter years.

Either one is overkill for this yard, 3/4 acre with some slope and no obstacles. Just want to future proof. For instance I have a 54" Super Mini Z for a 3 acre tree covered lot.

Any thought from the JD experts? And is a five minute warm up really required with the water cooled engine?

Thanks