Clustered servers or individual roles?
 

It is time to upgrade our servers.
What I would like to know is the communities opinion on whether the servers I pick are configured Clustered together or in a DB/Web Server setup.

We are on 3.x now and due to some custom integration with a drupal site I don't think we'll be upgrading to 4.x soon even though we have the licensing for it.

Currently we have a single server with Dual Xeon 2.66ghz and 3 Gigs RAM.
We are thinking of going to 2 servers with single i7 Processors and 4 Gigs RAM.

Lots of variables I left out regarding our system but this thread is for a discussion on the differences, good or bad, between the two configurations.