rod03801: Accurate isn't the right word there. Unless one is calculated incorrectly, they're both accurate, but let's not quibble... ;-)
Sounds like a good oppourtunity for a wager! I'd think that betting the median of the previous round would be better in general than betting the mean with the highs & lows eliminated. But, generally, I think one can stay below either average in the early rounds and build up a lead strong enough that the 'average' bidder would get into trouble sooner or later anyway, especially in larger ponds.
Of course I'm only rated 1642, so what do I know. ;-)