You mean what's better, a PCMCIA card with Firewire, or one with Firewire and USB? If that's what you mean, I say get the pure Firewire, your laptop has USB already, right?
Or do you mean what's better, a PCMCIA card with Firewire or some sort of USB 2.0 to Firewire converter? If that's what you mean I say go for the PCMCIA card.