Sir Kitc, If I just purchase the mixer then not use the usb but connect it to a soundcard is it much better or the firewire is still the way to go?
In both cases, you will only be capable of recording 2 channels of audio. Firewire is one option, a pci soundcard like the M-Audio Delta 1010LT is another if you need multiple input capability. Personally, though, I find firewire mixers to be a very flexible option because of the portability of the interface, meaning you can easily transfer it from pc to pc without much fuss, and at the same time, the mixer can function standalone.
As an interface protocol, I find firewire to be better in terms of speed, number of channels and cpu loading, so I think firewire really is the better way to go. USB2 interfaces are just as good but at the expense of higher cpu loading. I'm waiting for reviews regarding the Toneport UX8 to verify this, but Roland's earlier UA-1000 and UA-101 bear out the fact that these USB2 interfaces work quite well.