The 1/4" valve on the 3pt hitch is used on all of the Kubota BX's and all the B's except the Bxx30's. It is probably cheaper than the position control valve. On the equipment I use like the box blade it does not really matter. It goes up and down just fine with reasonable control of the speed. But when I use the rotary mower (brush hog), as I mow, the front of the mower gradually sags down so I need to ease it back up with the control. The rotorary mower has only one wheel in the back and the front is supported by the 3 point hitch. Out of curiosity I put my box blade on the back of the tractor. It weighs about 500 lb. In ten minutes with the motor on or off, the box dropped about 3/4" from the fully raised position. If you used a rear finish mower (RFM) it would not matter because it has wheels on all four corners, so it just rides on the ground.
The Position control valve used on the L models and
B2630 or 3030 will maintain the implement at a set height so the mower would not sag down. It also would be more easily repeatable to get an implement like a plow to the same depth on each pass.
When we test drove tractors, the dealer gave us the keys to a BX, the
B2920 and a
B7800. My wife and I each drove all three 2 times each. They even offered to get a
BX24 out of the show room as it was what we were considering. Make sure as bxowner says, you give them a good ride and get them up to PTO speed.
BXowner - German cars always have hard foam (MDI based). I have had an Audi and 2 VW's (My BMW motorcycle doesn't count). I know your pain but love their cars.