I'm just not into the chasis size thing, in some cases it's not even distinguishable. I did not even think about it until you mentioned it. Even JD's site will compare their "medium chasis" to I guess what is considered a Kubota "large chasis", even though Kubota never mentions this. The physical size of these two tractors is very similar. Tires, engine, even weight is not that much different and plenty of reasons can account for a variation in weights. My local JD/Kubota dealer had them almost side by side and quite frankly, it was the JD 4310 that I presumed to be the larger of the two. I will admit that some of the strategy is marketing, Kubotas local dealer freely admitted, people told Kubota they wanted bigger tires and more loader performance and in this case, it appears they listened. Two dealers both mentioned that they felt the 3130 would be a bit underwhelming powerwise knowing the hills I live on and knowing I had a L48. It's no secret that the smallest of their "large frame" will also have the smallest engine, but it is only 2 ft lbs of torque less then the L3430. I for one mentioned before, they really did not need both sizes, I would have just had the L3430 engine in a L3130 model. The L4330 and 4630 are another example. I believe the entire reason for that was to try and matchup against JD's lineup. The advantage of having the latest tractor on the market is that you can focus on the direct competition and beat them by gnats bottom and let the specification freaks go googoo. That's why I take the specs with a certain amount of salt. I don't believe it comes down to one company having to be right and everyone else wrong, it's simply a matter of choice. I took the liberty of comparing similar transmission types since our poster also expressed a lack of knowledge about tractors. The other thing and perhaps really the defining thing for me was when I went to price the two, they were very close with the L3130 HST actually coming in lower then the JD4310 eHydro, yet another reason the small, medium and large is kind of a blurry line for me. Anyway John, as usual, it's always enjoyable engaging in friendly conversation, your a wealth of knowledge. After visiting that photography site, you know DPR review, I realized just how bad a web forum can be and appreciate what goes on here. Thanks, Mark