We're talking theoretical here. Bitcoin's pool problem is temporary and being dealt with currently no PoS system is safe at all, that's why they have not much value. No guarantee with PoS because you have to trust people. Bitcoin only trusts math, If a 51% secret cabal took over any PoS, then it could take permanent control. Even if someone temporarily took 51% control of Bitcoin, then someone else could simply add mining power and take it away. With PoW, the permanent ability to 51% attack isn't even a possibility. With PoS it is inevitable.
There's so much wrong in your statement, I don't know where to start, let me give it a try:
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"currently no PoS system is safe at all"Actually, just the opposite. Currently no PoS altcoin has been successfully 51% attacked, ZERO! While plenty of PoW altcoin has been attacked to death.
Well altcoins don't really have much work behind them yet, do they? That's a poor argument.
* "If a 51% secret cabal took over any PoS, then it could take permanent control"
That's true, except you don't even need 51% of the eco-system in PoW, you need 0% of the coin, and at most 10% of the value of the eco-system, also you don't push up the coin price while you acquiring hardware, unlike in PoS, you will push the price up astronomically even acquiring 10% of outstanding coins. So attacking a PoW system is MUCH easier. Also, if someone manages to somehow owns 51% of the PoS eco-system (probably after spending an astronomical amount of money), they have zero reason to attack it, since they are basically attacking themselves, as they are the biggest stake holder in the eco-system, the only result would be destroying their own wealth.
You can try to double spend at any percent. If you try you will fail and probably be prosecuted for fraud. Even if you have a successful 51% attack, it is likely to be detected and you will lose your mining investment.
* "Even if someone temporarily took 51% control of Bitcoin, then someone else could simply add mining power and take it away"
Like who? non of the 51% attacked to death altcoins has shown this phenomenon, please give me some examples.
Altcoins can be interesting experiments. Many of them make unfounded claims and deserve their fate. Namecoin was spared this fate by merge mining because it serve a purpose other than competing with Bitcoin.
* "With PoW, the permanent ability to 51% attack isn't even a possibility. With PoS it is inevitable."
Except, again, ZERO PoS altcoin has been 51% attacked, so I'm not sure where this "inevitability" come from. Though I could say a PoW system being attacked IS inevitable, once the coin supply run out, and it become extremely cheap to attack. The Bitcoin PoW network is basically currently being secured by the coin supply, once it runs out, it's laughably cheap to 51% attack Bitcoin(unless transaction fees somehow become extremely expensive, and people would still accept that).
Wealth has a funny way of aggregating into a few families. With PoS, it can be quietly and secretly secured over time until only one person controls the majority stake. With PoW, people have to actually work to maintain wealth. It's not so easy to own human spirits.
There is a fundamental difference between PoS and PoW. PoS is aristocratic in nature. PoW is proletariat. It comes down to which side of humanity you choose to identify.Wow, lots of claims made here. Are you sure 51% attack is illegal in all countries? (or in any country at all? lol) otherwise the attacker could just concentrate the effort in one country, not sure how they will "lose their mining investment" if their only intention was to attack. Many PoW altcoin has been 51% attacked to death, I haven't heard anyone got prosecuted for it, or "lost their mining investment"?
Not sure what "altcoins don't really have much work behind them yet" means. In altcoins, it has been clearly shown that it's much easier to attack a PoW system, as no PoS system has been successfully 51% attacked, even though many of them exists, and some of them very tiny too.
"PoS is aristocratic in nature. PoW is proletariat"... wtf does this even mean, if we look at Bitcoin PoW mining power is extremely concentrated. discus fish and ghash.io controls at least 40% of the network, and several other large mining companies control the rest. While PoS distribution is usually much better, and this is demanded by the community. For example Peercoin, the largest PoS stakeholder address that is mining with his stake, has about 1% of the coin. Also one of the funny thing I observed in a PoS system, is that many of the stake holders decides to not to mine. Usually only about 10-20% of the coin actively engage in mining PoS.