The only statement that matters is whether you are familiar with either MySQL or LDAP. I don't agree with the other assertions about performance and distributed model of storage.
The MySQL database of users can be replicated so each RADIUS server query a local slave database. There is no bottleneck on a single database. (exactly like in a LDAP setup)
http://dev.mysql.com/doc/refman/4.1/en/replication.html
For example, the RADIUS servers on my site received yesterday 6 millions requests (auth + acct), and the servers were always under 5% of CPU usage. (Pentium 4 2.4GHz)
So unless you have good reasons, I think you should keep the MySQL solution if it works for you.
-- Nicolas Baradakis
I agree with that. I was previously stating what I liked about ldap. The most important thing though is being able to support it.