i think usb 2 will do just as good job as firewire (well not the new firewire obnviously)
scsi is not really an option for a home user he will need a scsi card and drive and large good ones aint cheap
i imagien sata is the way to go i have 3 scsi drives and 1 sata drive and im hard pushed to tell teh difference (except the scsi has a 5 year warrenty and sata 3)