Hi LSU,
Don't have first-hand information on either, but studied the specs extensively and looked into the features of Kubota transmissions while I was buying the
L4300...which is a basic gear tractor much like the
L3400.
The
L3130's GST is much more sophisticated than the
L3400's straight gear transmission. Clutchless shifting and Fwd/Rev. shuttling is possible with GST from what I understand. This should make it much more convenient to use than the
L3400. It will also make it much more complex and harder to repair as there are multiple electrical and (I believe) hydraulic circuits involved that must all be working for GST to function.
With the
L3400, you have a range shifter with High-Low-Reverse ranges and a four speed main gearbox. To shift you (should) depress the clutch, bring the tractor to a full stop, select your gear/range, re-engage the clutch. You should definitely do all this if you are shuttling or changing ranges. You can shift between gears in the main gearbox 'on the fly' with no difficulty, so you don't have to stop. Shifting between RANGES 'on the fly' has damaged range gearboxes as a search of the forum will show. This is less than convenient, but the mechanisms involved are very simple and not prone to rodent damage.
Beyond the convenience issues, don't forget that GST offers 12 forward gears and 8 reverse gears; while the
L3400 Gear is limited to 8 forward/4 reverse. Even better, the GST offers a creeper option that doubles the amount of forward and reverse speeds. Extra speeds (gears) can be worth their weight in gold in some applications like tilling and snow blowing when you need to carefully control ground speed, while keeping engine speed fixed at PTO RPM.
Although I'm one of the forum's gearheads, I've grown to love the HST on my
B7610. Unless you're heavy into ground engagement work, the L3400HST or
L3430/3830 HSTs (if you're worried about power loss) might be a good bet. Relatively simple while mucho convenient.
FWIW
Bob