I looked at the JD before I got my 2554. The JD is more finished or car like, however you want to say it. It might be nice for a wife to operate. It doesn't seem quite as heavy duty for some reason though. The JD has wider rear tires and an easier method of changing the cutting height. It has a 25hp Kawasaki engine instead of the 23hp Kohler but I don't see a real advantage there either way. The fuel tank is bigger on the JD and that would be an advantage. I can't get quite 2 hours of mowing with my 2554 before I have to stop for fuel. The JD also turns a little tighter even though the 340 is only 2 wheel steer. The Deere will also have higher resale value if you think you might be upgrading in a few years. But, the JD has a belt to drive the hydrostat instead of the bulletproof shaft setup on the Cub.
The things that decided it for me were the cost difference for what amounts to equivalent functionality, and the neighbors who own JD's. Without exception they told me if I were going to keep the tractor a long time to get something other than a Deere because of parts cost down the road. JD seems to price every part like it's part of a $250,000 combine and the only place to get anything is your local JD dealer. No internet dealers like the great guys on this board that can sell you OEM Cub parts. Plus, my local Cub dealer is a lot more service oriented and friendly to mower buyers than the JD dealer.
The $1000 difference in price since the local JD dealer won't move from retail, and the parts pricing were enough to convince me to buy the Cub. That was my reasoning anyway, but I'm sure you'd be happy with either one...
edit: one thing I forgot to add - As far as quality of cut, I don't see any way the JD could be better than my 2554. I have a friend who spent the last 10 years doing golf course maintenance so he's used to grass that has to be cut perfectly. He stopped by right after I got my tractor and immediately commented on how nice the cut was from the Cub...