WE/MI v102 was a community developed rebalance with official sanction. However, a deadline left too little time to fully test it before it was released as an official patch. After about a month of online games it became apparent that muskets and yari ashugaru were overpowered and monks a bit underpowered. Several of the same people involved in v102 along with some veteran players who were not involved in the v102 refined it further and released it as an unofficial v103 rebalance. In effect, v103 is what v102 was supposed to be as far as Sengoku Period games are concerned. You'll find that v103 offers better balanced muskets, monks, battlefield ninja, archers and yari ashigaru. All units have an effective counter unit and no one army type dominates. In addition, units were adjusted to fight longer so that there is more time to carry out flanking maneuvers making v103 more of a flanking game than v102 which is more of a shoot and rush type of game. The Mongol era games are still not fully balanced in the v103 with the Mongols being rather weak compared to the Japanese. There is a rebalance of the Mongols released as v105, but this was done by a single individual and did not get the degree of testing by top WE/MI players that the v103 got, but the Mongols are much stronger in v105.