I pretty sure you just made a typo when you did the title and put L4710hst, as kubota never made a L4710, I changed it.
Note: It's an 01 series, not 3900 or 4700 series.
the 39 and the 47 is the model class and HP class.
There is absolutely nothing wrong with the L4701, it's just the 01 series is geared more for the economically minded users.
So when it gets to the bigger HP models people tend to switch over to Grand L (60 series) tractors like the L4760, little more money and a lot more tractor.