Are there comparisons if is faster for beginners to learn to play on a isomorphic instrument?
Isomorphic is more logical and so easier to explain, but you still should be teaching the circle of 5ths to students. Once someone understands the circle of 5ths the layout of the conventional keyboard makes logical sense as well (it won't be as intuitive but the logic makes sense).
It might have some minor advantages, but there are probably also disadvantages: this doesn't help you learn the different modes (minor, dorian, etc.). Instead, they might be hindered by your muscle memory.
So, for comping it can shine, but for normal music, probably a disadvantage. I certainly don't see any advantage that should make everybody switch.
It seems to me that the standard piano layout (and the standard musical notation, which is basically piano tablature) is the result of cruft being added over time rather than refactoring to better express the underlying concepts.
.. these notes seem to work well for our gloomy church chants, let's call them A, B, C, D, E, F, G
.. hmm, maybe focusing on a more cheerful mode is better, so obviously we'll tell everyone to start from C rather than A
.. it seems that some of our intervals are roughly double the other intervals, let's add in the extra notes as C#, D#, F#, G#, A#, we won't bother telling the kids what happened to E# and B# though 'cause that's too hard to explain
.. 12tet incoming, we'll just retune our existing instruments slightly
Instruments and music theory are largely based around 12TET nowadays, but it seems like it's tacked on top of something else.
That depends on the constraints. Today's keyboard is a good compromise even today. You can compromise different things, but a full micro-tonal keyboard isn't enough better as to be worth it for most things and once you agree that you must compromise the only question is what. A 9:8 or 10:9 major second are both of rare use and so you probably just agree to get rid of them. The only hard part is 3rds, would you accept how bad they sound in a the current system (in which case a true 5th and a equal tempered 5th are close enough), or try to divide the thirds somehow.
A chromatic button accordion has other compensating advantages but I don’t find either one easier overall. They’re just different. You get better with practice.
I tune in all fourths as well. For me it has made a huge difference since I made the jump some years ago. Putting voicings, patterns, etc., into muscular memory is faster and a lot less work. For my purposes, it makes the instrument more intuitive with a better ear-hand connection. Even very advanced players trip on the G-B strings oddity (with things like playing a fast, angular melody on different string sets, without preparation, for example).