The "step-based locomotion technology" behind FIFA 14 makes the game feel grounded, putting a greater emphasis on the fluidity of movement. It's cool to see, because dribbling and positioning are paramount in soccer/football, so making the movement feel more than just moving the stick to glide players along the field is neat. Each step feels a bit more meaningful and just holding the stick in either direction lazily could give opposing players time to get into better position.
Beyond that, new ball physics allow for less linear shots, letting you truly Bend It Like Beckham as balls curve and drop in a more accurate manner. In addition, players approach shots in a more realistic way, cutting their stride as they approach the ball rather than doing weird, scissoring, stuttering leg things.
Iteration! Unless you're super into FIFA and wanted to buy it anyway, you might want to wait for the Xbox One and PlayStation 4 releases. Perhaps next year's Xbox One and PlayStation 4 releases when they get the next gen bugs ironed out a bit. Same could be said about most sports games, really.