After my own "March Madness" (maybe "September/March" is more appropriate as we demo'd 4 manufacturers in the fall and brought the final two back about three weeks ago), I have decided on Toro to replace a Walker mower on a large site we service. I am not sure if we should go with the Z593 diesel with the 23hp Kubota or the Z557 gas with the 30hp Kohler. Both units performed very well under the worst conditions. The units are on the same platform with only different powerplants. There seem to be more advantages to going diesel like better fuel economy, water-cooled, etc. However, I'm sure there are some disadvantages I am overlooking. I wanted to get some input from anyone who may have experience in either of these units or with the engines [in other machines]. Thank you!