Around here, tractor speak uses Category size as a general term for tractor size, and what it can do. For instance, the 70hp John Deere, in the picture above, is a "low end Category 2", and the 117hp MF is a "category 3". Yes, they do tell the size of the 3-point hitch, but hp sometimes overlaps the category sizes, so talking category just tells the general work that a tractor can do. Around here anyway, a compact tractor is not called a Category 1 tractor, but simply a compact even though the 3 pt. hitch can fit Category 1 implements.
Of course, there are many factors to consider in a purchase, but without information, that decision is limited.