From a resale stand point you should go with stainless steel, not corian. Corian is dated and also has the drawbacks that others pointed out (scratches easily, gets discolored/stains when heat is on it).
I'm a Realtor and I've seen buyers' reactions when they see a kitchen with corian and a corian sink (regardless of how new it is). They immediately think "dated" and start adding the cost in to switch to granite.
Hope this helps,