The difference in between the two is a matter of trust. Maintaining a 1:1 peg with the USD requires that users trust that the dollar reserves actually exist. Presumably, Coinbase will be seen by many as a more trusted 3rd party than Tether.
Stable coins exist to solve the problem of moving money in and out of cryptocurrency introduced by KYC/AML. Bitcoin represents an attempt to create a system of censorship resistant transactions with an absolute minimum amount of counter-party risk. Outside of the open cryptocurrency context, its unclear if something like stable coins would be allowed to exist. Certainly when you go back in history and look at things like ecash or the liberty dollar the answer seems to be no.
Stable coins exist to solve the problem of moving money in and out of cryptocurrency introduced by KYC/AML. Bitcoin represents an attempt to create a system of censorship resistant transactions with an absolute minimum amount of counter-party risk. Outside of the open cryptocurrency context, its unclear if something like stable coins would be allowed to exist. Certainly when you go back in history and look at things like ecash or the liberty dollar the answer seems to be no.