Sound guy, as always, sounds an expert on these old tractors (well, doesn't only sound, real.)
I am not so knowledgable, but, I'd study availability of aftermarket parts when chosing models. I don't know if their aftermarket parts of these old tractors are still being manufactured in USA or not (my guess is they are imported parts mostly and, mostly from Turkey.) So, reproduction situation of parts of these models here will be another factor for your decision. For example, MF 135 parts are easily available as there are many small manufacturing workshops still manufacturing their parts while parts for 230, etc are not mfg-ed by many. Ford 3000 parts too are easily available, though not as easier than MF 135 parts. This, new aftermarket part availability, is another factor, maybe, most important factor especially about old tractors.