[clairity]

sure, the difference is one of scale, but it's also one of purpose. the purpose of commuter rail is to be a spoke in a hub and spoke model. the purpose of intercity rail is to connect the hubs themselves. these superficially similar modes of transportation really shouldn't be contraposed, but if they were as in your argument, we should pick intercity rail over commuter rail because it tends to support density and walkability over sprawl (with all the environmental, health, and quality of life benefits that entails).

availability of land is a lesser factor for sprawl compared to reach. practically no one lives in suburban lands (like intraurban mountainscapes) unserviced by roads. sprawl is directly correlated to where we put roads, and less so to where there is open land. further, roads (and other infrastructure) are heavily subsidized, both directly and due to uninternalized externalities.

internalize all those externalities and we'd have much less debate on this topic. folks could simply choose what they prefer relative to actual costs.