I have spent considerable time looking at commercial mowers, including Exmark, Scag, Ferris, Grasshopper, and Kubota. I have narrowed down my evaluation to two mowers by Kubota, which I realize are quite different. One is the ZD331 and the other is the F3680. My application is a 15 acre piece that includes a range of circumstances, lots of rows of trees to go through and also scattered trees to mow around. It is more like park ground than residential lawn, but I want a nice finish in portions of it. Occasionally I pick up branches that could stall a blade, so the tilt up feature of the F series is very good. On the other hand, the ZD series has zero turn and offers better maneuverability. Since some of the terrain is not as smooth as you might like, operator ride and comfort are important, also. It seems that the F series rides better than the ZD, but then, in operating them, I am not sure that I would say that in a definitive way. My question is for owner/operators of F and ZD Kubota mowers. How do you compare these two models? What do you see as their strengths, virtues, disadvantages? Thank you.