> Deflationary currencies are good stores of value, but slow the economy (because why invest/buy now if your money gets more powerful the longer you refrain from spending it).

Logically speaking it is irrelevant; instead of holding gold and calling it money an investor can still hold gold except it gets called an investment; but their holding will perform the same way because it is linked to the value of gold. The practical difference is tax treatment which gets complicated. Theoretically if I recall expected inflation/deflation in the currency doesn't change the economic equilibrium because everyone just factors it in to the interest rates and salary negotiations to keep the focus on real value.

And in execution any consistent % inflation/deflation of the money supply makes things weird and confusing because the measuring stick used to measure wealth keeps changing.