Corian will stain and scratch easier than quartz but can be refinished. Chances are nothing will happen to the quartz but if it does the you are %^$#. Obviously,from a stain POV, you are far better off with cloud white. The tiniest imperfection will show on glacier white while cloud white will hide some tiny stain.
Squats are a functional physical activity, offering you spectacular benefits. If squats are performed consistently and with perfect form, they are one of the most powerful movements you can possibly do to tone your body.
Lunges work similar muscles to squats, but not exactly the same. You also have to remember that you're doing the same work, with all of your weight on one leg, rather than two. I find that lunges work the muscles on the inside of my knees more than squats.