Sub 300 miles the train should be faster door to door. Trains a better able to get into the middle of a city - airports both take a lot of space and are noisy so they get pushed to the edge of the city. Trains are also better able to integrate with a public transport system so they are easy to get to. Trains don't have the silly security lines (normally - though planes don't need them either). Trains also don't have large economic benefits from every seat full, so they can better handle someone making a last minute decision to go.
Note that I said should above. The reality is North America has terrible train service, and management (congress!) doesn't care: so airplanes end up better despite all reasons they are worse for short trips.
Note that I said should above. The reality is North America has terrible train service, and management (congress!) doesn't care: so airplanes end up better despite all reasons they are worse for short trips.