I went back to the dealer today and took the L3400 for a ride. The fit and finish of the B3030 was way over the L. They stated that the L series is due for a rebuild either this coming year or the next. I had a chance to look at them close to each other. The L is a little larger than the B which may be a issue for parking it in the garage.
Even with capacities that are nearly identical, the L3400 is a larger frame tractor than the B3030.
I can't see doing things like safely lifting a 5x6 round bale like I do on my L3400 on a B3030. I think that the extra weight and frame size of the L3400 makes it better for some set of tasks and the B's lighter weight and smaller frame make it better for another set of tasks.
I don't disagree that both the B3030 and the Grand Ls are more refined than the very basic and lackluster 'economy' L3400. It does what it does reasonably well however and has a pretty important place in the Kubota line up. I think Kubota sells A LOT of the L3400s.