Everyone here in the Yanmar forum will tell you based on personal experience that Yanmar's quality is excellent.
Because YM135D is a US model, its unlikely that a used one has had the bogus 'lipstick on a pig' reconditioning sometimes seen on tractors imported after a first lifetime in Asia. (and often misrepresented as low hours, new, or under 10 years old). That bogus reconditioning is about the only thing to be wary of, on a 35 year old Yanmar.
You might start a new thread inquiring in the Kubota forum, then decide if it is cost effective to consider a BX at what I expect will be far higher price for similar capability.
Anybody know what is the Japan-market Yanmar model same as this US YM135D?