Yeah, the speed of VMs in terms of pretty much everything except for graphics (and some other specialized hardware) entirely depends on the virtualization tech and the hardware you're running it on. I don't have any first-hand experience with VirtualPC, but from everything I've heard, it pretty much sucks performance-wise. VMware's offerings and VirtualBox offer much better performance (and they're still free ...well, Server and ESXi from VMware are..all their other stuff is pretty expensive).
yup. VirtualBox is IMO the best free desktop virtualization product on the market.