Can't say a wb is faster when its larger then a ztr.
Can't say a ztr will be cut more grass because it goes at a higher mph then a walker.
Selecting mowers involves access through gates an other obstacles.
Handle steep grades.
Lawn tractor is the way to go because it allows one hand operation.
A while back a poster needed to buy a mower because he had injured his shoulder, needed an operation, would not be able to use one arm for many months post operation. So his ztr was useful as a boat anchor to him that season. Why buy a mower twice?
Why walk even if you are young?
Remember it's years of wear and tear that takes the toll on your legs.