You are right, the MF 35, 135 and 235 are near identical copies of the Super Dexta of another color.
Look thru the upgrades, and you will observe that most of them are also done on the MF tractors. For instance the MF came with cartiride filters, as did the early 1000 series Fords. Don't see too many people trading tractors because of filters. Realizing that MF all came negative ground, but the starters, the oil spin on filter are just upgrades from the ferguson line. Same with the exhaust.
I can afford to spend a few dollars on my Super Dextas. I own four Super dextas, and for what I payed for the four, I could maybe buy one MF 135.
Forgive me, but not one piece of equipment I own has not be upgraded. I am a mechanic, not a collector, and some upgrades are just logical because I am a mechanic.
Like the first time I saw someone trying to jump start a Dexta.