Repairing or replacing a concrete floor
If the old floor is mostly sound and only has hairline cracks or a few chipped spots, a repair or a thin overlay is usually the better buy, because the slab underneath is still doing its job. If the floor has sunk, broken into pieces that move, or keeps lifting the covering you put on it, I'd replace it. Anything laid over a failing slab fails with it. I'll tell you which one I think your floor needs once I've seen it.
What shapes the cost of a concrete floor
Size is the starting point. After that, it comes down to whether an old slab has to be broken out and hauled away, how much digging and packing the base needs, and what goes under the slab for your covering. Rebar, the steel that helps a slab carry weight and hold together if it cracks, costs a little more than a plain pad. If something has to give, please trim the finish before the base. The base is hidden on day one, but it's what keeps a floor flat.