Lots of folks in the same boat, want to save a little $$$. Kubota talked about an aftermarket "equivalent" fuel filter (referencing th L3301, 3901, 4701, and the MX's) a while back, going on to say that the "equivalent" filter only filters down to I think 15 microns, where the Kubota filter will go all the way to FIVE microns. They also went on to say that if an aftermarket filter was installed, and the engine suffers a fuel system failure directly related to dirt/junk entry into the fuel system, they can deny warranty help. Worth mentioning especially since the fuel system on these things is EXTREMELY sensitive to dirt/dust/poo entry-and if you ever have to pay to have one repaired, you'll beat yourself up pretty good. Not to mention the cost. A fuel rail is about $1500 by itself....pumps are considerably more, PLUS labor, gaskets, etc.
And on the other filters, I have personally witnessed an aftermarket filter's comparison to a Motorcraft when I did Ford's, and then again when I briefly did GM stuff, and the Motorcraft and AC demolished the "equivalent" filters away in EVERY way (flow restriction, particle pass-through size, filter media durability, construction, drainback valve, and canister construction). After seeing this, it's no wonder the other"equivalent" brands are cheaper; it's because they're cheaper.
"Equivalent" does not mean "same". To my knowledge, a Kubota filter has never failed due to a filter defect. John Deere on the other hand......we won't go there.