If you have a gig of RAM I wouldn't run either of them. If it installs and runs correctly at all, it won't be able to access all of your ram. I just had a new Compaq P4 in here with a gig of ram and ME wouldn't even boot on the machine. Had to either take it down to 768MB or less or Install Win2K instead.
Of the other 2, I really noticed no speed difference personally. ME had better driver support maybe. I ran it for 9 months with no problems. Less problems than I'm having with win2k actually, but those are all driver related.