Spectrum is definitely the more widely available of these two providers. It’s available in a number of areas that Frontier isn’t—even including the Frontier DSL service. This makes Spectrum much easier to recommend for rural users, because they’re more likely to have Spectrum as an option. But Frontier may not be available or only available as slower DSL.
Frontier is available in 25 states, primarily in the North-Central US, with smatterings of service in the West, Southeast, and Texas. The vast majority of this coverage is DSL, with some fiber mixed in, primarily in metro areas.
Spectrum, on the other hand, is available in 42 states, with solid coverage in most regions of the country. Spectrum serves rural areas quite well, providing service to a number of areas that may not otherwise have high-speed internet access, including Frontier.
Of course, if availability is a concern, or you’re in a very rural area, you may have better luck with a different type of service altogether. Satellite internet is an excellent off-grid internet option due to its nationwide coverage, while 5G home internet is gaining ground quickly as a viable alternative in areas that don’t have high-speed infrastructure.