Due to the algorithms being inefficient
If that is resolved then the entire history will be suspect
And any thermodynamically similar future will have to compete on constants and exponents
Or you could regulate the hardware, 'this blockchain is only compatible with, and so calculated on, a gateway lt1700 with exactly 640k of ram' ;P
> Due to the algorithms being inefficient
This is by design, when the hardware gets better Bitcoin network starts requiring even more work, so being "efficient" is actually what is not desired here. See: https://en.bitcoin.it/wiki/Difficulty
>the miners must select one chain to mine
I am pointing out that the "sloshing" is in fact perfect evidence that they are only mining one chain at a time, or splitting their hashpower to varying proportions. This is completely normal and healthy miner behavior, they are simply greedy actors looking for the most profit. They cannot however mine both chains with their full hashpower for free (as you can with PoS), and this is an essential understanding when analyzing the security model of a consensus algorithm.
Also, the oscillations are most commonly exploitable only when the difficulty adjustments happen very quickly (see: BCH's EDA), so if 70% of the hashpower left, even if 16% of the remaining hashpower was malicious, the efficacy of a 51% will be handicapped by the disproportionately high difficulty.
I don’t care whether sloshing is “normal healthy behavior”. I care whether a fork has become easy to attack. You seem to focus on every topic but that one.
Original comment: "Also, with Proof of [Work] you get protection against an explosion of too many hard forks..."
My reply: "That's not what happened with the Bitcoin Cash fork though ... any given time, one of the networks is easy[er than 51%] to attack."
If you're not disputing that point, then you're not refuting my objection to that original comment.
Adding layers of complexity like Ethereum's Casper to solve the incentive incompatibilities caused by the nothing at stake and long range attacks do not address the fundamental issues, as consensus then require users to agree on a list of bonded validators (for which there is no switching cost). "Phone a friend" consensus is objectively weaker as a security model compared to POW which just requires users to validate the rules and calculate the chain with the most work.
POW is secure because it requires energy from outside the system to be provably burned. It's thermodynamically sound in that respect. /u/nullc recently described POS as a logical tautalogy which I think captures the issue well. If chains were a car, Bitcoin would be fueled by gas and a POS coin would be fueled by the leather on the seats. You're not going to get very far.