You definately want to record to a hdd other than your system drive. This is a good idea no matter what platform you're on.
I'd advise an internal SATA drive since they are faster than firewire. Of course this will limit your mobility. Ideally you should get both SATA & FW. Since your files are never really safe unless they are in more than one location I'd recommend getting both and keeping your files backed up on both, work off the SATA & use the FW for mobility and backups.
Seagate 7200.8 are great for large storage capacity & reliability.
The Western Digital Raptor 74GB 10k SATA drive is the fastest & only 10000rpm SATA drive, but is very $$$$$$$.