Not really, the security is the same.

You just make the work for attackers a bit faster=>cheaper.

But IMHO for an experienced attacker it's just a matter of "a bit faster" (like their attack comes a few days earlier), not a matter of "being more secure" (like their attack doesn't come at all).

You don’t know. I can tell you that that my colleagues have found cases where major vendors don’t “fix” a defect - they prevent the public exploit from executing. With open source, you can see exactly what was fixed and how.

You don’t lower or raise security.

Using the word "lower" here implies you're comparing open source software to something (closed source software), in which case you'd be implying that closed source software is engaged with and reviewed by security conscious developers.

If you think that's the case just because you've heard of a few high-profile open source vulnerabilities, I've got news for you...