The sealer used over a Decorative Concrete surface or Acid Stained floor is one of the most important things to consider when planing your floor.  Sealers come in many types and all of them offer different things over the other.  There is also a big difference in price between sealers.

Water Based sealers are low to no odor and they are easy to apply.  But, they provide the lowest level of protection to the floor and generally do not provide much enhancement to the colors.  These sealers also don't hold up well on exterior surfaces.

Solvent Based sealers are one of the most widely used sealers.  They penetrate into the concrete and form a clear film over the floor.  These sealers provide good scuff and UV protection as well as great color enhancement.  However, the odor of the solvent may make their use impractical in some areas where the smell will affect people or animals.

Epoxy Sealers come in water based and solvent based versions as well as 100% solids two-part systems that are 100% VOC free.  Epoxy sealers are a high build system good for bearing heavy loads and they offer a good "deep" look to the surface.  But, epoxy can scratch easier than many other sealers.  A moisture test should be done before an epoxy is applied because they do not breath and rising moisture vapor greater than 3 pounds can affect the adhesion to the surface.

Urethane sealers also come in water based and solvent based versions.  These sealers provide good color enhancement and give a deep look like epoxy.  There may be issues with odor on some versions and some do not breath.  They are very scratch resistant but require several days to cure before the area is available for use.