Edwards25519 is designed to make the cost of a discrete log computation cost at least about 2128 bit operations to break the first of any number of targets.
Edwards448 is designed to make the cost of a discrete log computation cost about 2224 bit operations to break the first of any number of targets.
Of course, since 2128 bit operations is already infeasible, edwards448 is really a hedge against modest cryptanalytic advances.
Per https://crypto.stackexchange.com/a/67468:
Of course, since 2128 bit operations is already infeasible, edwards448 is really a hedge against modest cryptanalytic advances.