I would say go either way.

I use a Ethernet connection at home, but while working I've hooked various computers up using a USB connection, both are capable of giving the speeds needed for broadband connections. So either way your fine with speeds.

It is true though that Ethernet is allot faster than USB, but as for home internet connections go right now, they can't keep up with the speed Ethernet offers, so USB is a good alternative, because it is still above the connections we currently have at hand.

The only real problem with using USB instead of Ethernet, is the other USB devices. USB is shared bandwidth, so if you are using a bunch of USB devices plus being on the net, for each device hooked up, it will cut the USB bandwidth in half. Unless your running like 4 or 5 devices I don't think you would notice any change in the internet connection though, but this is one problem you might want to consider.

Especially since you can go buy an Ethernet card for like 10 bucks.