Does anyone know if there are only personal preferences between the two IMAP servers or does one of a slight advantage over the other? I've used Dovecot only in the past but my package manager loads tons of MySQL libraries with Dovecot which is a problem since that's not authorized on my server right now. I can either install it from source or try another application like Courier.

Use Dovecot. If you are familiar with Dovecot, and try to use Courier it will make you cry.

+1 for dovecot from here too. I've used courier before on one system and when I tried dovecot on other system, I don't want to go back. Easy to set up and very flexible IMO.

It's always personal preference but Dovecot gets my vote.

+1 for Dovecot here too. The installation and configuration is much easier. I suggest that you read several how-to installation documents. Make sure that you understand what the options are doing and the syntax of the configuration files. Spending the time go gain a level of understanding before you try to implement will really pay off in the long run. Dovecot has pretty good debugging functionality too. Getting it to co-ordinate the authentication against a SQL database can be a little tricky at times, so don't be afraid to use these features.