I manage a server for a client who has several Wordpress blogs. They all precariously balance on PHP/FastCGI/nginx and it all works at the moment, just using a little more RAM than I'd normally be comfortable with.
Since setting this all up, Wordpress 3 came out and (with a plugin to maintain domain mapping) allows me to import all the blogs into one central blog. So I know I can achieve a desirable operating outcome... I'm just not sure if I want to sink hours into doing it.
The client now wants to add a couple more blogs to the server. We're clearly at a crossroads where it would make sense to act now if I'm going to go down the multisite road.
I don't really care about the clear administrative benefits rather the performance and the amount of free RAM.
Do you think I would be correct in assuming one codebase in RAM would cost less than having half-a-dozen single sites? Are there any other performance pros (or cons) that I'm missing?