Alot sharper but much more fragile (and tougher to make in bulk).
This is a key point. Once the technology of smelting and casting is learned, large numbers of virtually identical arrowheads, mace heads, and other weapons or tools can be made from metals, by relatively unskilled people. Flint knapping is much more of an art than a technology, an art that depends on careful selection of raw materials, detailed understanding of how silicified stones like flint and chert fracture, individual skill, and many more man-hours per tool are required.
However, the knowledge of flint knapping did not completely die out (or was rediscovered) and was resurrected for the manufacture of gunflints. Also, because knapping is more an art that requires high skill, I could also see it survive as a means to produce high-status ceremonial weapons or ornaments in early bronze-age cultures - and possibly longer. One has only to see some of the Classic Maya "eccentric" flints to see what a flint knapper can produce.
It is also worth noting that, among the high cultures of Mexico and Central America (which remained at a "stone age" level), the manufacture of chipped stone tools emulated the mass-production techniques of metalurgy: For most utilitarian and military applications, carefully shaped points and spearheads gave way to simple unshaped blades and flakes that could be produced in large numbers by large numbers of tool makers, many of whom could probably not have made a Clovis point if their life dependend on it. The artists among them made high status or ceremonial objects.