To begin with I have own Case, currently own two Kubotas and one John Deere. Only my Kubota B2710 is about same size as you are looking at. We do have a strong NH and Kubota dealership within ten miles or me with the NH also a Kioto dealer. There has been a Kioto dealership near me for at least ten years. This is only my observation but there are at least a many small Kubotas all other brands together. By small I will say about 50 hp and less. JD is about 20 miles from me.
I have operated my brother in laws 3000 JD which is an open station tractor and found it a stable, strong tractor. For looking to the rear I do turn to my right and the fel joystick was being pushed by my right knee which bugged me. Only negative I found. It did have only two range hydro trans, I was using it with fel and box blade and found no problem with the two range trans. Was on rocky sloping Texas land and not our rock free and basically flat land.
I have friend who's boomer broke in half and know that has been issue with some model of the Boomer, look for that even at tractorbynet. Believe it was due to either FEL or Back Hoe without the proper frame on the tractor. On the few comments have really heard on the Kioti is not major issues just nagging ones. Not aware of any issue with the compact JD, at same time not that many as either of the Kubota, NH or Kioti.
Last year I was with my nephew as he was looking at a new Case 75 HP tractor with four wheel drive, cab and front end loader. It was right at $44,000. We left there and went to a JD dealer to look at what they had and I priced a 4044 R with same options as the Case. WOW, same price! Only difference was the JD had hydro trans, smaller frame tractor and 31 hp less.
I am in process of retiring from my small farming operation and looking to the JD 4066R, Kubota L6060 and Yanmar YT359. Each with cab, hydro transmission and fel. So far the JD is the highest price and I am willing to pay more for the JD than the others just due to experience my JD farm tractor compared to my Kubotas. However for me am leaning to the Yanmar at present.
Said a lot to get to this: No idea on the NH nor really the Kioti as not seen new one in about four years. Look at each option on each tractor. Compare the weight of each one carefully. Also specs on the fel. Doubt in that size tractor but in the 4000 series JD they have better selection of FEL than I am finding on the other brands. Look at how the fel attach and remove if possible as some fel are not removable and some buckets are not quick connect or change out to other options. Read your comment not seeing them in cab, sure would be great if you could sit in their cab for I find there is differences in them and comfort and your size or habits might make a difference. Do your best to verify support after the sales. I think the JD has a Yanmar engine but verify.
Only valid reason can think of major price difference is JD only has the tier IV while the others still have the tier 3.