I used the big ones, Bigger is better.......right? I can't think of any real reason for one or the other, weight? Not much difference really, Room? plenty....
The big ones will require more fluid I guess.. You decide... your car.
Alex, I'm using the big ones on my SL-C, lots of room and as Howard said, "Bigger is better". It really does not matter, both sizes are packaged by Wilwood for your convenience when fitting for different applications.