Plywood Versus Particleboard Cabinet Boxes
What the box is actually made of
Three substrates account for nearly every kitchen carcass sold: veneer core plywood, industrial grade particleboard, and medium density fibreboard. All three arrive as a sheet, get bored on the same line and end up wearing the same melamine or veneer skin. Once assembled they look close to identical. They behave very differently.
Screw holding
This is where the gap is widest. A number 8 screw driven into the face of 3/4 inch veneer core plywood typically withdraws at somewhere around 350 to 450 pounds. The same screw into the face of 45 pound density industrial particleboard sits nearer 200 to 250 pounds, and into the raw edge it can fall under 150. MDF lands between the two on the face and does surprisingly well on the edge because its core is uniform rather than a lattice of chips and voids.
That matters at exactly four points: the hinge plate, the drawer slide, the mounting rail that carries the wall cabinet, and any wall cleat. A well built particleboard cabinet solves this rather than ignoring it, by using confirmat style fasteners with a coarse deep thread, by adding a plywood or solid mounting strip behind the hinge and rail, or by using cam and dowel joinery that loads the panel in compression. If the line you are looking at does none of that and simply drives a coarse chipboard screw into a bare edge, that is the finding, not the substrate itself.
Weight and handling
A 3/4 inch sheet of veneer core ply runs roughly 65 to 70 pounds. Industrial particleboard of the same size is closer to 95 pounds and MDF is heavier again at around 100. Over a full run of base cabinets that difference reaches several hundred pounds bearing on the fasteners tying uppers to studs, and a heavy upper is harder to hold plumb while one installer drives the first screw.
Under the sink
Water is the honest test. Plywood exposed to a slow supply line drip swells at the affected plies, may delaminate locally, and can often be dried, sanded and kept. Particleboard swells irreversibly. The resin bond releases, the chips expand, and a saturated deck can gain a quarter inch in thickness and never return. MDF fails the same way and often faster because the fibre wicks. In a dry inland valley like Yakima the ambient risk is low, but a sink base sees liquid water rather than humidity, and liquid water does not care about the local climate.
The practical fix is not the substrate, it is the sealing. Look for a factory finished deck, a fully banded edge at the cut for the plumbing penetration, and ideally an integral pan. A raw unsealed hole saw cut through a melamine deck is a wick pointed straight at the core.
Edge banding
Every panel product needs its edges closed, and this is where cheap work shows first. Thin 0.4 mil paper tape applied with hot melt chips at the corner and lets go with steam. A 1 mm PVC or ABS band applied on a proper edgebander with a trimmed and buffed radius survives normal use.
Sag over a span
Shelf deflection is a span problem before it is a material problem. A 3/4 inch shelf of any of the three is fine at 24 inches. At 36 inches under a load of dishes, particleboard and MDF will take a visible set, often 1/8 to 1/4 inch, and the set is permanent. Plywood at the same span sags less and recovers more. Adding a 3/4 inch by 1 1/2 inch nosing glued to the front edge stiffens any shelf enough to erase the difference, which is a cheaper fix than upgrading the whole carcass.
Cost, and the fair verdict
Plywood boxes usually add ten to twenty percent to the cabinet portion of a kitchen. That is real money and it buys real things, but particleboard is not automatically bad and the reflex to treat it as garbage is wrong. Industrial grade particleboard is flatter than plywood, has no voids, no core telegraphing and no internal stress, so it stays square and takes a melamine surface beautifully. What separates a good particleboard cabinet from a bad one is density, thickness, the fastening system and the edge treatment. A 45 pound board at full 3/4 inch with cam and dowel joinery and 1 mm banding will outlast a thin voided import plywood box every time.