I looked at the same two tractors last year. Pricing on the JD was about 10% higher than the Kubota. The JD has a few more features, like position control and QA bucket, plus independent PTO clutch. I've heard people say that the operater station on the Deere was roomier or more comfortable than the Kubota - this I don't understand. While the the pedal setup on the JD is different (I actually preferred the JD setup over the Kubota setup - but have since gotten used to the Kubota setup and like it) the operator platform on the Kubota is much cleaner and larger than the JD. The old B series was closterphobic in terms of size, but that is not the case on the new B. The clutch setup on the JD is a premium feature that Kubota should have included with the B series. But the one overiding feature that the Kubota has that the JD does not is the 3 range hydro. This was the deal breaker for me. I use my machine primarily for mowing. I really wanted to get the JD, but the fact that it would not take any sort of incline while mowing was something that I could not live with - and yes, I did drive the machine, albeit at the dealer's place. The low range speed on the JD was slower than that on my old garden tractor. The mid range on the Kubota is considerably faster, has enough power to take the steepest of hills, but is not so fast as to be uncomfortable when mowing.
It all depends on your needs, and how the machine will perform those tasks. The JD has a few premium features that Kubota only offers on the B30 series - but the Kubota is cheaper and has a three range hydro. For my needs, the three ranges was more important than the missing features. Whether that will be the case for you, only you can decide. The deciding part is a lot of fun, so take your time and enjoy it - you might not need to ever do this again! Both machines are excellent, and will probably outlast me and you!