This is where the money quietly goes. Refinishing a hardwood floor costs far more than either tool, so the wheel and contact details matter more than the capacity most of the time.
Furniture dollies concentrate weight onto four small casters. A 400 lb dresser on four 3-inch wheels is a lot of pressure per square inch, and any grit trapped in a caster becomes a cutting tool dragged across your finish. Two defenses: buy non-marking wheels — the Mytee specifies non-marring TPR, the Rubbermaid specifies non-marking casters — and wipe or vacuum the wheels before the first indoor trip. Carpeted decks help the furniture, not the floor; they also trap the grit that does the scratching, so vacuum the deck too.
Hand trucks put everything on two larger wheels plus the nose plate. Bigger wheels spread the load better and roll over thresholds instead of stopping dead at them — the Harper convertible’s 10 inch pneumatic wheels are the friendliest thing here on rough ground or a tile lip. The risk moves to the nose plate, which is a steel edge that drops onto your floor every time you set the load down. The Harper appliance truck specifies non-marking vinyl facing for exactly this reason.
On carpet, both struggle, and sliders win. Small casters sink into pile and steer badly. This is the case for the third option: X-PROTECTOR’s carpet sliders are 4-3/4 in across specifically because the larger diameter spreads the load so it does not sink. Their hardwood set is 3-1/2 in external with a 2-3/4 in internal face, felt over rubber foam, reusable with no adhesive.
Which leads to the honest recommendation most dolly articles will not make: if you are moving something within a room or across one floor of a house, sliders are frequently the right tool and cost under $15. A dolly is for transport, not for repositioning.