Credentials vs portfolios isn't an either or argument. And "worse" is a loaded term.
If you have the credential of an undergrad degree at MIT with a good GPA, combined with a credential of working for Google for 5 years, there is a very high likelihood you are a good engineer.
On the other hand if you have made serious contributions to the Linux kernel, there is a very high likelihood you are a good engineer.
But most developers don't go to MIT and work at Google. And they also don't make serious contributions to large open source projects. For most developers credentials and portfolios are not effective methods of hiring.
There are certainly problems with the portfolio model, but I've never heard anyone seriously argue that it's worse than credentials.