I was wondering if the only difference between the two kits is the
thickness of the rotor: Serious Street (12 x 0.81) & Sport (12 x 1.10).
I have heard that the sport kit will move the track of the wheel
out 0.4 inches, and I am wondering if this would look staggered
compared to the rear wheel. Also, I know the difference in price
is only $10, and would like to know the advantages of the
sport over the serious street setup.

 

Check my sig, the additional offset is not visibly apparent.

As far as differences off the top of my head I thought the caliper was different, too.