I have the impression that if that Fergie were a diesel it would be called TED20, not TEA20. Forming an opinion on second-hand equipment from photographs alone is a hopeless quest, especially when they are around 60 years old. The difference in prices between the two is somewhat indicative, though the front loader on the Kubota might increase its value by $2k.
Essentially these two examples are at opposite extremes: the TEA20 is as simple as it gets, being based on an almost unmodified Standard Vanguard car engine and fairly rudimentary tractor equipment. The Kubota is a modern machine with 4WD, and has parts and service readily available (at a price). One is a collector's item, the other a convenience item. Depends what you want to spend, and how much convenience you want. In between these extremes there are various less-elderly Fergusons, and even some TEAs and TEDs that have been retrofitted with Perkins engines. Why don't you try driving a tractor or two in an actual work situation, at some neighbour's property?
