I have a Mac Pro and all the internal drives are used up. I am about to start editing a project and I'm working if I should buy USB drives or a firewire hub and use external firewire drives?

I am buying 1TB Setgates.

Any suggestions?

I don't know Macs, but could you buy an eSATA card and use eSATA drives? If so, that would be much faster/better.

you think it would be ok to capture the footage to usb drives for now and then later transfer everything to eSATA drives when editing?

Well first off I wouldn't be buying Seagate drives. I've seen way too many fail to let you! USB isn't fast enough. You need at least FireWire 400 with a 7200 rpm drive. Because you have a Mac Pro, you can easily get an eSATA card (or even a RAID controller) and plug your drives in that way. If you are editing really big files (like RED 4k) look into getting an SAS enclosure, like the Editbox 8ML and a RocketRaid or CalDigit controller card.

I went ahead and got a sATA PCI express card (2 x sATA) and a black widow external sATA dual drive dock and 2 Seagate 1TB barracudas. Seems to be working fine.