This is a very open-ended question. There is a wide range of types and quality of sealers, and the process and skill and attention to detail of the applicator also comes into play. Some fabricators may also not even seal it (although it should be for a kitchen countertop). It depends on how the fabricator sets expectations for the client regarding the sealer and concrete. It also matters if the expectations of the lifetime and maintenance of the sealer has been set for the client--and upkept. It also depends on the quality and finish of concrete used and the skill of the fabricator, just as much as the sealer and upkeep. Concrete is never as simple as black or white--- there are also many shades of grey.

Are concrete and Saltillo tiles your only options? Would you consider slate? It is probably the least expensive of the stone options. Concrete is not handsome and it can crack.

Professionally done concrete stains look fabulous. DIY, sometimes not so much...

DuraCeramic, High Density Ceramic (both of which are frost proof, unlike regular ceramic) or porcelain tile. When you stay stamping are you stating the outside patio concrete was stained? If the concrete is stained you will have to have the stain and sealer removed before any tile can be laid.