It's a fixed deck machine. As opposed to a floating deck. A 48" fixed deck wouldn't give quite the quality of cut needed for the residentials you will be cutting. And the extra width would keep you out of enough places that your trimming time would increase and you wouldn't be any further ahead.
Don't sell the 36" short. With a Kawasaki twin cylinder engine it's a lot of mower.
The stander is a clear advantage over a WB & sulky combination. And I don't even own one myself. But I've watched my competition, and tried them out at the EXPO. Every manufacturer is coming out with a stander. They are THE way to mow.
You may not need a stander the first year. But it's something you can grow into. It could easily earn a mower payment, car payment, provide you with spending cash and even put something back for college.
But what you need a stander for is for the day you clear about $400, and you say "gee; I'd like to do that tomorrow too!"
Sure you could save maybe a thousand bucks, buying a WB. But you'll earn that extra thousand the first summer. Then every summer after that the thousand goes into your pocket.
Go to a dealer. Try one out. You'll see what I'm talking about.