PoS is far more advanced approach since it demands much less electricity. However, this approach is good when it's applied from the first days of project's life. Live migration from PoW to PoS is very painful since it demotivates miners and inevitably leads the project's to its fatal split.
I think POS is only advanced with respect to its "greener approach" to mining
With respect to a coin, there just aren't proper POS (and MN) models that work as well as POW models. If you browse the altcoin announcements the few kind of POS models that show up:
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Fully POS, you need to buy the coin with btc/fiat in order to be able to "mine". So you're basically asked to invest money in order to get a higher stake probability. What people don't tell you is that you can very easily be out-invested in this model because of the increasing coin supply over time (you own less coins vs total coins) AND the amount of "big spenders" that tend to increase for staking. This means that you sit with the problem of your network weight decreasing over time.
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Hybrid POW/POS, only rewards the initial POW contributors tbh. But because of the nature of POS, their POW shares gives them such a vast control over the coin during it's lifetime that it will be very hard to compete unless you buy their shares out. And in this case, these POW contributors can choke the supply if they wanted to, which is a form of centralization
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Masternodes I have mixed feelings about. They seem to be a fair approach so far and the coin yields seems to be distributed evenly over the number of MN's in the network. I suppose that this way, the only way to yield more coins is to buy more MNs which seems to be a reasonable ask. For me the key balance here is the collateral required for a MN. Too low and then everybody is a MN. Too high and then there's only a few MN which rewards the early adopters
To me, POS are very weighted towards its whale buyers. MN can be done in a manner that's fair. My main thought principal is that cryptocurrency was always meant for everybody, so some layman with a scrappy old machine would always get the opportunity to mine and gain coins. Yes, there are centralization attempts like mining farms and ASICs (nothing wrong with these btw); but it's not like your old machine vs an ASIC, you can join a pool and still get rewards. And when a coin gets popular, it's increasingly harder to get centralization over it via mining (unless you're XVG LOL); making it more fair than POS.
While I appreciate POS's green concept, it's just that the current currency/financial models feel very biased towards big spenders, which I feel causes centralization.
I think the only fair POS approach I found in a coin, and I am not sure I can even call it POS is with NEO. There, you get GAS from holding NEO even if it's just 1 NEO. And that is something that's guaranteed unlike a POS network which has your rewards as a variable.