If the hashing algorithm is slower, as most altcoin algorithms are, it is a disadvantage because it takes more processing time to validate a block and increases the number of organic re-orgs makes it easier to double spend.
Proof Of Stake In Proof of Stakeinstead of sacrificing energy to mine a block, a user must prove they own a certain amount of the cryptocurrency to generate a block.
The more stake you own, the more likely you are to generate a block. In theory, this should prevent users from creating forks because it will devalue their stake and it should save a lot of energy.
Proof of Stake sounds like a good idea, but ironically, there is the “Nothing at Stake” problem.
Because mining Bitcoin is costly, it is not smart to waste your energy on a fork that won’t earn you any money, however with Proof of Stake, it is free to mine a fork. An example of a nothing at stake attack is an attacker buying lots of “old stake” from users inexpensively inexpensive to users who no longer have stake in the currency. This can be made convenient by offering small payments to users for uploading their wallet.
Eventually after accumulating enough “old stake”, the user can begin creating blocks and destroying as many or more coin days than the network was at that time.
This block generation can be repeated until it catches up to and beats the current main-chain very cheaply. There are also “stake grinding” attacks which require a trivial amount of currency. In a stake  grinding attack, the attacker has a small amount of stake and goes through the history of the blockchain and finds places where their stake wins a block. In order to consecutively win, they modify the next block header until some stake they own wins once again.
This attack requires a bit of computation, but definately isn’t impractical. Below, we’ll explore some of the possibilities. Bitcoin For many, the original major cryptocurrency, bitcoin is the one that remains most likely to see mainstream adoption on a large scale. While there is no single authoritative list of companies around the world that accept digital currencies like bitcoin, Coin Telegraph suggests that 54 major companies currently accept one or more digital currencies.
Of those, just two don’t accept bitcoin. In this way, bitcoin has outpaced all other digital currencies currently on offerand in this way it is the most usable digital currency in the mainstream business world at this point, at least when it comes to payments. Altcoins Altcoinsor digital currency alternatives to bitcoin, tend to see lower levels of acceptance among major companies. It’s important to keep in mind, though, that a list of 54 companies is far from exhaustive.
For this reason, it’s helpful to look to other resources to get a glimpse of where things stand.