Different markets have different preferences, and there is a strong demand for both deck sizes across the U.S. In some markets contractors will only use 48" mowers while other markets prefer 52". We're glad you appreciate the advantages of Toro's 40" deck, we've received similar comments from other landscape professionals.
Technically speaking 52" decks offer two advantages; wider cut (which you identified) and in some cases improved trimming. While 8.3% or 2 minutes per lawn may not seem like much, over the course of the day/week this can really add up. In the case of Toro mowers (we can't speak for other brands) our 52" decks are more offset outside the left drive tire providing improved trimability. This improved trimability along hardscapes and around beds and landscape structure can significantly reduce time spent on the jobsite string trimming.
Toro feels similarly regarding the exclusive ride and walk benefits of our Toro GrandStand mower. This two-in-one versatility can reduce the investment, maintenance and trailer space associated with an extra mower. You can rest assured Toro will continue to take into account the special demands of southern turf.
Thanks for your comments - The Toro Company