I can't speak first hand with the newer models. Went in to pick up a few parts for my ZD331 and was looking at one of the new ones- not sure what the number was. One of them is still offered with a 72" deck that the sales guy said might not be a great idea due to the lower HP, may want to look into that and get some opinions if you want a 72" deck. Personally I would have preferred a 60 for the quality of the cut, but I have a lot to mow so the 72 made sense for me.
Having a fuel level indicator on both tanks would be great, but I would still prefer to use only one side at a time. I top off after I'm done to limit condensation in the tanks, having to always top off 2 just means a little more work. I have to mow quite a bit to have to switch to the other side.
I did not notice the profile of the tires, but I like that mine have quite a bit of sidewall to absorb the unseen ruts and bumps. The seats on these are also quite good.
These are solid performers no matter what you decide, mine has almost 800 hard use hours and I have mostly only dealt with maintenance things. A starter wire worked loose and gave me fits, also dealt with water in the fuel system last summer. Other than that is has been good.