In terms of game modes the game has everything you need in a Warriors title and then some. Story mode of course is for all the characters in the game. Free mode lets you play any level with any character (including created ones). Historical Mode lets you take your created character and use him/her to join in the war for Japan.You choose which missions to do and interact with other characters as you forge your own path in Japanese history! Marasame Castle mode is a mode like the board game Sugoroko mode in the previous installment. Its kinda fun but I haven't spent much time with it because the other modes are just more entertaining to me.
Id like to add something about the games difficulty, and this goes out to all Warriors titles in fact. The games seem very easy to most players and while that is true for the most part. These games are also unbelievably challenging if you play it on Chaos mode. I dare you to try and take out Lu Bu in Dynasty Warriors 5 Hu Lao Gate level on Chaos mode. Its the same in SW with Tadakatsu Honda, and the same in the Orochi series with Orochi. So before you classify the Warriors series of games as just a mindless hack n slash that takes no skill. I urge you too try what I just said.
In conclusion I will say that if your not a Warriors fan in general then don't bother with SW3 because its not going to swing your vote. If you think they are decent games then give it a shot because like I said, I think this is the best one since Dynasty Warriors 3 on the PS2. If you are a Warriors fan then your probably already playing it!