[Zope] User Source choices

This is a bit off-topic, but I wondered if anyone has any opinions on the matter. I'm going to use LoginManager for my user folder stuff, and I'm wondering which type of DB to use to store user information. Has anyone any advice about this? Here's some of the free choices with what I know about them: MySQL is my first choice because I know it well postgres has transactions, stored procedures, but can scale badly SyBase I know nothing about LDAP (e.g. OpenLDAP) is optimised for this kind of thing, but I'm not sure I've quite grokked it yet Should my choice be dependent on the quality of the adapters available, or are all the adapters much the same? any comments appreciated, seb