If we can limit the discussion to the genuine Neumann U47 product whose only variable is the tube (and all necessary circuit/component alterations) then I can tell you from my 30-year personal experience:1. None of the alternatives you mention will recreate the magic of a VF14 mated to the existing U47 circuit/capsule. And the reason is quite obvious: all the tube you cite are cheaper and more readily available than a VF14. That is the ONLY reason anyone has ever looked at any of these alternatives, not because they would yield superior audio, regardless how you define superior.2. UF and EF 14, while somewhat related to the VF14 in construction and outline, have an overheating handicap which is only overcome by feeding a second voltage into the mic- a major mod. While these tubes can theoretically be biased in a similar way as the VF14 (fixed) the less noisy option-cathode biasing- will yield a substantial deviation in sound- thinned out, glassy, quite transparent, yet leaning towards body-less. 3. As soon as you exit the steel-tube world and look towards some of the high quality Telefunken designs like EF86/806/804 etc. you get into trouble with the existing transformer configuration: a bad match.I gave up after these and similar kinds of experiments, and realized that the U47 and VF14-combination is a match made in heaven, and should be left alone. There ARE enough VF14 out there, but an increasing number of U47 seekers feel a five figure price is too steep for their pocket book (understandable), and are lured to substantially cheaper supposed alternatives by posters who claim authority- sometimes individuals with a vested interest (not understandable, in my book). I do not wish to devalue the role U47 copies, re-interpretations, etc. can play for buyers who simply are not in a position to shell out five figures for a fifty year old microphone- some of these U47-inspired mics are quite nice in their own right- but I caution anybody who is after "that" sound not to fall into the trap discussed by hobbyists and eternal U47 wannabes: there is no substitute for the VF14. Period.
Yes,I can comment that, despite repeated promises by representatives of Telefunken/USA, I have not received a tester of their glass tube-in-a-metal jacket they call "VF14k". I can therefore not make any statements what such a tube would sound like.