It depends on your clients. A lot of my clients have a 36" gate I have to squeeze through so having a 48" would be useless for me. I don't know if this applies to you or not.
Floating decks also move up and down with the terrain so they don't scalp. If the lawns have a lot of holes and uneven terrain this might be good. None of my accounts really need it, except 1 area on one of them, which im aware of and don't scalp.
You should be able to find a good used walk behind, like exmark metro, or exmark turf tracer if you want floating deck / hydro on craigslist. I bought my used 36 metro for $1,500 with 200 hours, it has worked great. I also bought a velke for it so now I don't have to run behind it.
A lot of people in my area also use scag, they are good too.