I sure regret using the word only.

Perhaps I should have used the word preferred

MMIO WAS 'preferred', in the days of external code and data memory, today when, due to the internal Flash and RAM, in most cases, you have all port pins availble I doubt many would 'prefer' MMIO.

but then I would be answering the question "Preferred by whom?"

No need, preferences are totally subjective.

Now, if you want to regreat again, you may regret not using "I prefer", instead of "preferred" :)

Erik