In early game I never "rush" for samurai units due to recruitment time and cost. But later on I opt for balanced army of katana+yari samurai, but usually keep my archers as ashigaru, giving emphasis to the number of arrows rather than firing speed or accuracy (accuracy is of course improved by encampments and fletchers).
Then to top it all off my superior army composition, which I spend time acquiring and use to capture Kyoto, has 2-4 units of finest yari cavalry with incredible charge bonuses. These are just for the reason that I circle around my enemies and then charge through their archers. Their charge is actually so good that I can make them run through enemy archer unit with little to no casualties, enemy is left with more than 35% losses and I'm already preparing for the next charge.
Wedge formation is of course a must for this strategy.