Rear brake rotor size

70% of your stopping power is in the front.
Rear brakes are almost always smaller by a little bit

Fwd?

Front wheel drive, rear wheel drive, mid-engined: it doesn't matter. Weight transferrance means the front wheels carry most of the weight under braking and therefore have more powerful brakes than the rear. Motorcycles are mid-engined and have more powerful front brakes (usually twin discs) and less powerful rears, and when you ride you press the rear brake pedal lightly and do most of your stopping with the front brakes.

Agree. I ride motorcycles too. If you use the rear brake too much you will lock it up and fishtail. Front brakes on all vehicles do most of the stopping.

Hehe, I ride motorcycle too, and my Z1000 does have twin disc... I just never thought about it.

I learned something new from you guys that will help me out once I start to ride.

Riding I use at least 70-80% of the front brake exclusively. Much greater stopping power, no fish tailing and no sliding.