The only difference between the cryptocurrency being issued by private company or a country is that the country can't technically go bankrupt and the coin can't become a scam. But if we think about value, then it depends how the certain coin will be backed.
I dont know about the other coins but for me bitcoin is the best coin, I think all of us should invest at the moment, now all over the world almost all companies are issuing the bitcoin to their employs, it is good progress to our income with our investment, scamming happens because of our carelessness if we will not show carelessness so we will only earn no one can scam our bitcoin.