Well...it really comes down to this: a LAN chipset is only as good as the interface that it is connected to. A PCI NIC will have roughly the same performance as a onboard chipset connected through the PCI bus, and a PCIe NIC will have roughly the same performance as a onboard chipset connected through the PCIe bus, but a PCIe of either will KILL a PCI of either, even if the bus is only of x1 width.
Now, moving on to your question of brands...I've never seen an Intel onboard chipset, so I really can't address that, but, both Marvell and Realtek make good stuff, so you're fine with either. Just remember, PCIe > PCI.