That's a fun one! I am going to bank of most people not having a clue what's you're talking about. I would head over to the CentOS wiki, they have a tutorial that is pretty solid.
Depending on what you need to do, you may want to even considering checking out the Cluster Suite. It may be overkill for you but will give you some other options.
Is it better that HAProxy, meeh, I think it's more of being a different approach that being better. It depends on what you want to accomplish. HAProxy is going to give you front-side load balancing for spreading load across multiple servers. DRDB is going to give you HA storage for multiple storage.
The question would be what is your primary objective? Are you deploying HA to prevent a storage outage, or are you deploying multiple servers for availability? If you can give me some more insight on what you want to accomplish, I could give some more guidance.