For shared hosting companies, what is more important to have more of installed on your server?

1. CPU
2. Memory

Also, what are you finding to be today's avarage config for your servers to fit around shared hosting 300-400 sites

Depends on your workload but more often drives and memory outweigh the CPU especially with the newer processors.

I would always go with loads of ram, but it is true it depends on what your users will do, if they will have big mysql databases and stuff.

As the others said, depends on the average traffic, and what kind of websites they are.

They are shared hosting sites. The average site you can assume runs a PHP/Mysql forum, blog or something.

I would look to upgrade RAM before CPU, also due to the fact that you can then open up your Apache/MySQL and other service configurations a bit more, to offer better performance from having access to more memory.

As mentioned it does depend on the type of sites being hosted. A few users consuming excessive CPU brings the performance down drasticly for everyone else, its vital that it's monitored.

You can get some powerful CPU for cheap, so concentrate on the RAM upgrade wise, unless you plan to host massive amounts of MySQL intensive sites.

CPU is more importance for shared hosting.

For the average server, you'll usually run out of RAM or disk I/O resources before you ever max out the CPU. The CPU is one of the last things I would upgrade.

They are shared hosting sites. The average site you can assume runs a PHP/Mysql forum, blog or something.

RAM :agree: