Both forks may live on. That's what happened with Etherium. Etherium Classic is about $2, and holding relatively steady, with a market cap of $176 million. Forked Etherium (as modded to bail out the DAO) is around $50. (The market cap for Etherium is kind of fake, because the coin generation rate is very fast, and many of those coins are locked up for some period of time.)

Although the difficulty adjustments in Bitcoin are much slower than in Ethereum.

The chain with the smaller hash rate is unlikely to be functional for a long time (unless new miners step up but this would be a tremendous investment).

This is by design as this makes it economically unfeasible to fork the chain and suddenly have twice the amount of coins.

Some have. No merchants have. So if you pay by bitcoin to bpay, your china-coin isn't going to be recognized. You would need to find exchanges that recognized the china-coin tokens. 97% of nodes in the bitcoin network currently enforce the same consensus rules. As soon as bitcoin forks, they will no-longer understand, nor view, the tokens in their forked crypto-coin. You might, or might not, find someone who is willing to trade with you.

I think it's around 90% use core and 10% use unlimited. There aren't that many full nodes.

The only ChinaBU nodes are living on centralized server instances, and none are actually used for bitcoin commerce. The software is unsafe. No exchange, wallet, payment processor, or user, would dare dream of using it. Which is why hundreds can disappear in the space of an hour, and re-appear 12 hours later all at once.

But to clear it up, there are thousands of nodes. By some measures, when including non-listening nodes, 10's of thousands.

I'm running a full BTC Unlimited node right now.

Good for you. Let's hope the chinese exchanges eventually let you trade the china-coin you'll be holding after they fork-off.