Under NetBSD, at least, a 100 Mbps card has less overhead in an Amiga 1200 than a 10 Mbps, but the difference isn't huge - the top transfer speed is just over 700k/sec in a mostly idle system as compared with the 10 Mbps card which was about 600k/sec.
I'm using a Dlink DFE-670TXD which is an NE2000 card.
