"he ran both machines for a couple years and learned them the same. do ya think there would be any advantage either way?"
One 'advantage' would be for the other consumers who would be interested in the person's in-depth descriptions of what he/she had learned during that span. Certainly there would be questions such as:
In two years did you split the use-time evenly between the two detectors?
If so, which of the two did you prefer, and why?
If you favored one over the other most of the two years, what were the reasons?
If you used one of the two about 75% of the time, why would you even care to use the other for the 25% balance of time?
Which search coils did you use on each model, and what did you think of them?
What types of sites did you hunt?
Which model features seemed to be the most beneficial when using that model?
Did not having a display cause a problem in results?
Did using the F75 display seem to benefit you in any way?
How much did you rely on the visual display of the F75?
Ignoring any visual display, which model provided the better overall audio response?
By the time the user compared their own use and results over a two year period, and once they answered these typical questions that an active hobbyist might have, then you (and the user) would know what 'advantages' there might be.
I am sure that if it was a stranger to the hobby and they were just trying to learn how to use these detectors and where-to and how-to hunt, some would really like the simplicity of the 1270. Most manufacturer have gravitated to making visual display model either exclusively, or almost. The exception here in the USA would the the Tesoro brand. Over time they got a good following behind them, and up until maybe 10-15 years ago it seems they still drew a much better percentage of users. Their attempts to compete with a Target ID model have basically been quite terrible in performance, but their non-display model have been somewhat popular ... before.
After two years I think most users would have grown to prefer the F-75. partly due to the visual display, but also due to the difference in adjustment functions, the Tone ID choices, automated GB and manual GB, and other newer features.
Currently you have a Fisher 1266-X, and a Tesoro Tej