Both "hold the tech". A PCI-E 2.0 interconnect requires both a PCI-E 2.0 video card and a PCI-E 2.0 slot on the motherboard. That said, on most motherboards, PCI-E 2.0 is backwards compatible, so a PCI-E 2.0 card will work on a PCI-E slot and a PCI-E card will work in a PCI-E 2.0 slot.
Performance differences are next to non-existant on all but the most powerful video cards, to boot.