Fabric, metal mesh, or plastic J-channel — what's the difference?

Plastic J-channels are the cheapest and stick directly under the desktop, but they have limited depth and rely on adhesive. Metal mesh trays carry the most weight and ventilate heat from power bricks well, though some reviewers note they can scratch desks and are awkward to route. Fabric trays hide cables most cleanly and are gentle on furniture, but they're harder to access once everything is loaded.