...you sure it was on Full Duplex? Because Ethernet speeds far surpass the speed of the DVD drive itself - if it stuttered, it'd mean it was unplayable on disc.
Yep. Ethernet may be quicker, but ps2 does not seem to utilize full speed. Transferring games to hdd, you get at best 3-4MB/s transfer speed (which is why most say connect hdd directly to computer to transfer), compared to near 10MB/s that you get when transferring games to the 360 over network.