Many websites offer the option to log in with your existing Google or Facebook account (among others). For a long time I've resisted doing this because I use a password manager and I figured it was more secure to create a separate account for each website with a strong, pseudorandom password. The browser integration for some cloud-based password managers is great, and I started to wonder why nobody had created a server-side version. Then it dawned on me that federated login basically is the server-side equivalent of a password manager (assuming you don't reuse passwords for the password manager).
Purely from a security standpoint, is there any good reason why I should prefer creating unique login credentials and storing them in a password manager vs. using federated login, or vice-versa? (assume I want to use a cloud-based password manager)