I think they all work fine and are more or less well balanced (although board no. 8 seems to be strong)
I too find #8 the strongest board. It has lots of small areas at the border for many early bonus points, including a potential player order lead due to the ships. And a nice big pasture on top for large points near the end.
However, we also include no. 1. Waerbaer, why not? Is it too weak?
We usually played this board for all players when introducing new players; and since i'm a member of a large gaming club, that has happened a lot.
And i don't like the fact that the castles and the mines are all together. Getting all 3 early for the points (and all the mines for coins) is just too straightforward.