When you have a game series with as many titles as this one, you start to try new things. Xillia lets you choose between two different protagonists, and the scenes you see depend on who you chose.
I admire this decision, and it is things like this the series should keep trying, to make the series fresh while still retaining the core of what makes the games great.
The battle system also lets you link with other character to provide support to each other, which offers some combat variety.
The world, characters, and story were all brilliant. So much so that it prompted a sequel in Tales of Xillia 2.