Every second warehouse manager we meet has been quoted for both, usually with wildly different numbers, and no one has explained why. The honest answer is that the two finishes solve different problems, and the slab underneath decides more than the brochure does.
Polished concrete: cheap to own, fussy to start
Polishing uses the slab you already have. Diamond tooling cuts the surface, densifier hardens it, and successive passes bring up the sheen. There is nothing to peel because there is no coating, and maintenance is a scrubber with clean water.
The catch is the slab itself. If the concrete is soft, patched in twenty places, or was power-troweled too hard, polishing will show every one of those stories. We take a scratch test before quoting so nobody is surprised.
Epoxy: a new surface with rules
Epoxy builds a new wearing surface on top of the slab, which makes it the right call when you need chemical resistance, a colour, or a seamless washdown floor. It also hides a slab that polishing would expose.
Epoxy fails for two reasons: moisture from below and poor preparation. Vancouver slabs often sit on damp ground with no vapour barrier, so we test relative humidity in the slab before writing a spec. If the reading is high, a moisture-mitigating primer goes in the budget from day one.
Downtime, honestly
Polishing is dry work and you can often run in one half of the building while we cut the other. Epoxy needs the area empty and clean, and standard systems want 24 hours before foot traffic and 48 to 72 before forklifts. Polyaspartic topcoats shorten that dramatically but cost more per square foot.
A quick rule of thumb
Dry storage, decent slab, tight budget over ten years: polish it. Chemicals, washdowns, colour coding, or a slab that needs covering: coat it. If you are somewhere in the middle, a densified and sealed floor with epoxy only in the wet zones is usually the sensible compromise.