Note that the OP said "total travel time during the day", implicitly saying that the time between e.g. 11pm and 5am doesn't count.
For the O/D pairs served by Amtrak in 8-10 hours on the LD network, redeyes aren't commonly available, so the flight alternative would be something like fly out earlier and stay overnight in a hotel or get up at zero dark thirty to catch the early flight.
Consider Rochester, NY - South Bend, IN on 49/449:
Amtrak: Dp Rochester 11:12pm - Ar South Bend 8:49am +1
UA: Dp Rochester 7:00am +1 - Ar South Bend 10:54am +1 (via ORD)
- Dp Rochester 5:30pm - Ar South Bend 9:44pm (via ORD)
AA: Dp Rochester 6:17am +1 - Ar South Bend 2:08pm +1 (via CLT)
- Dp Rochester 1:17pm - Ar South Bend 7:42pm (via PHL, CLT)
DL: Dp Rochester 6:00am +1 - Ar South Bend 9:47am +1 (via DTW)
- Dp Rochester 5:36pm - Ar South Bend 9:28pm (via DTW)
AA is a joke here. UA/DL vs. AMTK, for a let's say 11:30 am thing in SBN:
* out the door around 4pm and fly the evening before: 19 hours in airport, plane and hotel
* wake up at 3-4:30am (probably damaging your evening plans) and fly in the morning with a hub connection: 6 or so hours and you're possibly already beat when you show up
* have a normal evening (likely on the train by midnight), get a free drink in the lounge, sleep, and have breakfast (possibly even shower) on the train: 12 hours door to door, but you were asleep for a lot of them
Different strokes and all that, but you can see how it could work.