If your ever driving around town, Look around for a Lawn Care Company that are moweing yards....
You will find most using,
Grasshoppers,
Scags (Best)
Toro's,
Dixie choppers,
all Zero turn, and range in price form $7,000 up to $25,000
I know these are alittle overboard for a home owner, But you did as for the good ones...
For the johnDeere's being around for years, (Farming) Yes they have been.. But you need to compare apples to apples.... Alittle rider lawn mower is in whole differant ball game than , (Lets say)
4010
4020
3010
4030
4440
So on and so on.... These are (Farm Tractors).... Not for the home owner... And out of the ones I mentioned above the 4020 and 4440 are the best...
Our 4020 is a early 70's model and runs like a champ.... the 4440 is anewer one with A/C..............
Good luck in what ever you deside to buy...
P.S. IMO, from what your dad is describing that he would like in a mower, I think a (Cub Caddet) would be his best bang for his buck... Build solid, and have the Kawasaki motor in them....
Check what gage steel is used on all the little riders mentioned above, and check the Cub Cadet.... You will find it to be double the thickness... (Thinner guage= rust, dents, welds that break)....
Matt