(The issue here is probably not what
they are made of, assuming it is not MDF but rather how good the fasteners
are and how the facings are attached to the cases. Cabinets that fall apart
usually shed their facings.)
For me - the what they are made of matters because: I am the klutz that let
water drip through the grout (groutless) part of ceramic tile countertop. Now
part of the countertop sits a bit higher than the other. Don't want that to
happen again. It's the reason for the new cabinets, too. The water caused
swelling in another place and the door is permanently "ajar" about 1/8 in. but
I can see it.
Thanks for your help anyway.