I'm seeing these metallic media case tumblers around for about 3x the price of the old school walnut or corncob media ones.  I'm wondering what is the difference and why are the metal ones worth so much more?

I think your seeing the wet media tumblers with pins.

I have both, a Dillon tumbler and a rotary style SS dawn/lemonshine system.

The SS pins will restore brass to like new condition. It will scrub primer pockets and the case interior as good as new. There is a downside.

It gets the brass so clean that bullet seating is harder. It comes out wet and you will have to figure out a way to dry it.

Since I clean prior to resizing I simply tumble the brass in clean corn cob media to remove the lube. Adding a cap full of Nu Finish car wax to the corn cob introduces a little lube to the neck interior to help with bullet seating.

Nobody needs SS pins to clean brass adequately well. Everyone has to remove lube from resized brass regardless of which system you use. It's perfectly okay to run corn cob through your SS tumbler provided it's dry inside.

Forty years ago I was one of the few people at my club that actually tumble cleaned their brass. Everyone always commented on how good my reloads looked. Everyone else just wiped them off with a rag.

You need to keep dirt out of your dies. You need to get resizing lube off of the brass. As long as those minimum requirements are met you will be fine.