Just so you know when most of us are talking about ZTR's we are talking about 52" to 60" with suspension seats and a ride much better than the one you got. Also you have to grow your business towards lawns that are more wide open. I don't blow clippings into beds, I generally mulch and with the right combo of water and fertilizer the lawns look great. If someone has an area they want bagged I have a 60" with a bagger that I can use but rarely need too. I carry 3 large ztrs and a 21" for tight spots, small gates on my trailer. That way I can mulch bag or side discharge with 3 different setups. I don't bid lawns with gates that would keep my ztr's out, I don't want them. I'm getting older and find this works best for me. But for comparisons I don't think you would see any benefit of using a 48"ztr compared to the walkbehinds you mentioned. ZTR's need to be 52" to be worth it. You get more trimside, and in general wider tires to support the weight.