MD5-CRYPT/CRAM-MD5 vs SHA512-CRYPT/PLAIN

Hello,

I am wondering which variant is more secure for user authentication and password scheme. Basically I am looking at both variants:

1. MD5-CRYPT password scheme storage with CRAM-MD5 auth mechanism
2. SHA512-CRYPT password scheme storage with PLAIN auth mechanism

In my opinion the option 2) should be safer although it is using PLAIN auth mechanism. Of course I would always use STARTTLS and not allow unencrypted connection.

What is your opinion?

Best, ML