Hi Tosh,
I've tried using USB for this but I have to admit that I am unsure what you mean by USB 2 as I've not heard of it before. All I can say is that the Firewire card I installed was a godsend. I use the Pinnacle software like you and have found that by connecting my camera to my PC via the firewire card it is quicker and also easier.
A good thing is that I can control the camera from the PC by using the little control panel that is displayed on the Pinnacle software and the response is instantaneous. Based on this I would recommend that you use a Firewire card. Mine cost £30 and the cable was another £15. I imagine that you can probably get a better deal than I did but make sure you check that you get the correct cable to link your Firewire port to your camera as there are different varieties.
Again, I am not entirely sure what you mean by USB 2 but assuming it is the same as the USB on my PC (which is 2 years old) then go for the Firewire, if it IS different then I don't honestly know.
If it is different I would like to know more as things like this do interest me.
Cheers.
SuperOwl