43 Hours on the Amtrak Southwest Chief
Between train and plane in Europe I will almost always choose train hands down. Oftentimes the trip time is comparable. Train station are in the city center, so it's easy to book the hotel in the walking distance. For plane it is a taxi to the airport, two hours at the airport, flight time, luggage collection and a taxi to the hotel. Up to 500 km speed train would be faster, and up to 1000 km it is still more comfortable.