I needed a custom set of shelves when I renovated a bathroom a few years ago and I used melamine.

All the things mentioned above were encountered as problems along the way, chipping, trying to hide the joins, etc.

end product looked fine, I sealed all the interior joins afterwards with white bathroom silicon and it was very tidy.

the whole process was a nightmare I wouldn't wish on my worst enemy

I have a new set of custom shelves I need to build in this house (just outside the kitchen for all the low use appliances) and I plan to use MDF

I think plywood for a bedroom closet would look great
I've seen some very nice walk-ins finished with a pale stain (classy)