Stop in for a cup of coffee

How to Determine the Size of the Cutting Deck Needed for a Riding Mower Lots of trees and things to mow around? I would get the smaller one but that's just me.
I do have a lot of trees and a 48 inch deck is what I was thinking.
The current owner planted 80 trees 25 years ago.
Several of them only have a couple more months left.