Which bus has the best read/write performance for small files when used with an external drive? I'd guess eSATA, but the MacBook Pro in question lacks an ExpressCard slot. So it comes down to either USB2 or FireWire 800.
The reason I'm asking is because I want to run Ubuntu Server virtualized (through VirtualBox) on an external hard drive. I'll only use it for web development (Apache, MySQL, PHP) so the reads/writes should mainly be of smaller files.