I have a 27 Kohler carbed engine on my 60" Super Z and a 26 EFI on my 60" Lazer. My 26 EFI is probably one of the "problem children" you may have read about. Although I think it is fixed now, I still don't know whether or not I would buy another one.
I believe the Kohler you are looking at for the Super is, in fact, a 28 EFI rather than a 27. Now for the low down. My 26 uses less fuel than my carbed 27. Seems to be about 25-30% less in the couple times I have actually tracked usage. I will keep more logs of this though to try to determine exactly how much less over time. Let's use the 30% number for now. If I use it 1000 hours over a couple year period, I might save $450 dollars on gasoline figured at $1.50/gal. Versus the 27 carbed engine, the 26 EFI would be a much tougher sale for me on a Hustler. Especially after using both engines, albeit on different mowers. With the Exmark, you are getting the suspension seat when you buy the EPS with the EFI engine. My 27 Hustler already has that so it's not part of an option package. Now comparing a 28 EFI, to the 27 is a different story. In theory it should be 3 or 4 horsepower stronger, and that certainly makes it more attractive than the 26 EFI.
I would look at the facts. How many hours do you think you will put on it over the course of your ownership? How much is gasoline where you are at? How much extra is the EFI engine going to cost you? Do you have solid parts availability on Kohler engines? If you lose a fuel pump, are you going to be able to have a replacement in a timely manner? This could go either way, so I am sure you will come up with your answer. Basically, if I were putting 1000 hours a year on a new machine, I would probably get the 28 EFI and just trade in or sell my mower(s) every two years. That way the engine would be under warranty and you would really take advantage of the EFI.
