This article, this article, and this earlier question indicate that, given enough satellites in LEO, it's possible to substitute between GEO and LEO. The first article and the question have some indication of the substitution ratios (from the article, 40-80 LEO sats to 3 GEO sats; from the question, 100 LEO sats to 1 GEO sat) for what seem to be telecom applications.
My question: For which applications are LEO and GEO substitutable?
I'm assuming telecom and imaging are among them; is that correct, and what else might be?
Any thoughts or suggestions would be much appreciated. Thank you!