I really enjoyed my
M6800. It was a very good tractor, and after driving a friend's New Holland, I thought it was also a very refined tractor. Now that I have a John Deere, I realize how 'rough' the Kubota was. Remember, I'm only comparing an open station Kubota to a top of the line utility cab John Deere... the John Deere's controls are laid out very intuitively. Within 15 minutes of driving the John Deere, I could already place my hand on all the different controls without looking. It is a nicely laid out cab.
The gear shift on the John Deere has a nice tight pattern with a light throw. The first time I drove the tractor I was shifting from 1st to 3rd and wound up grinding gears. I had to stop, look at the shift pattern and try again. The problem was the Deere's throw between gears was much, much tighter than the Kubota's. Where 3rd was on the Kubota was where park was on the Deere!
The ride is very comfortable. The steering also has a better, lighter feel. It really feels like I'm driving a large car rather than a tractor. Cycle time on the loader is quick and in general, it has a lot more hydraulic power than the Kubota.
John Deere does command a higher price tag. Part of that is the John Deere name. The only other vehicular brand name I know with the recognition of Deere is Harley Davidson. I don't know of any other brand (selling planes, trains, boats, helicopters, cars, bikes, or tractors) that has a John Deere or Harley Davidson type store that sell nothing but swag.
We got a pretty good price on our John Deere and I'm very pleased with the product. There were some teething pains, but the dealer bent over backwards to fix them. That is a lot more than I can say for any Kubota dealer I've ever dealt with (local issue only and not a reflection of Kubota as a whole).
The Kubota is a good tractor. John Deere is a good tractor. In this case, the 5425 is a much better tractor than a
M6800. That might not be the same depending on which model is compared to which across the manufacturers' line-up.
I think we're all very lucky. There are a ton of good tractors out there which means we have a lot from which to choose. That isn't a bad thing. For me, the 5425 was the best fit. For someone else, it might be a McCormick, Mahindra, New Holland, Duetz, Kioti, Jinma, Massey, Montana, or some other brand.

I wouldn't mind owning one of each!