Why would you reinvent the wheel when there are so many closet systems out there that have parts and hardware necessary to assemble a well-designed closet? Unless you have tons of money, melamine is the way to go because it doesn't have to receive a finish after it's built and easy to clean.

http://www.easytrack.com/

http://www.easytrack.com/browse/pantry-organization/

https://www.walmart.com/ip/Easy-Track-24-W-Closet-Tower

http://www.simplyneu.com/

Now they offer LED lights in the rods though it requires electric run to your closet. I would definitely consider the lights. Too hard to tell black from blue sometimes.

Plywood is the strongest option and that's what I'd put in my closet. Just make sure that if it spans a length longer than 30" that it's got a support in the middle.

melamine should do the job

Baltic birch plywood is a good alternative, depending on your other finishes.

If you decide to go with your carpenter's suggestion, first ask about the alternatives for treating the plywood edges to be sure you like what you're going to get.

The shelf in my closet also is part of the support for my closet bar. The brackets are screwed into the studs and the shelf above. You may not be putting anything heavy ON the shelves, but if your closet rod hangs from it, you'll be putting plenty of stress on it. Melamine won't stand up to that, it's very easy for the screws to strip out of them.

You guys are awesome! Thank you for all the feedback!

Plywood installed by even a semi skilled carpenter will look better and last longer than any of the modular options out there. No brainer to me.

I think plywood will only look better if it's a high end veneer, has veneered or solid strips on the front edges, and has a durable finish. I have a melamine closet system in my master BR that looks brand new after 15 years. I have high end CVG fir plywood cabinetry in my living room and kitchen, which looks good, but is showing the inevitable wear and scratches here and there.

I assumed that the OP's plan was to paint the units. In which case basic $30-$40 sheet plywood from HD and $1 a foot poplar 1x2 trim would be fine. I am a woodworking hobbyist and that's what I used in all the closets in my house. Pick through the stack at HD for clear and straight wood, sand, prime, paint. Looks good and will last forever. If it gets nicked up or looks dated you can repaint. If the plan is to stain and poly the wood ... that does significantly increase the cost of labor and materials. You would need higher quality materials and the carpenter would need to have more skill, spend more time and have better tools. Good luck.

I like the ELFA system from The Container Store. As your needs and wardrobe change you can reconfigure the closet space.