As the pp said, it depends.
I use Amtrak whenever I can, as it saves wear & tear on me.
The San Joaquins go up the center of California and I am able to relax or work when I go the SF or Sac, and don't have to deal with parking.
We took the Coast Starlight and Empire Builder to Minnesota last year & will be taking the Sunset Limited to New Orleans this year on the way to WDW. [We would go all the way if the route had been fully restored post-Katrina, but even with the tracks fixed there is still debate on the issue
]
I treat the train as part of the vacation. If you are in a quick hurry, it may not be the best choice...unless if you were driving and would have to spend the night you are able to keep moving while you sleep [something most of your passengers would not prefer in the automobile
]
I like the freedom to walk around, get something to eat, use a bathroom...all the while not being stuffed into an airplane seat and herded like cattle. If you book a room, meals are included.
If you plan to use Amtrak, book early as prices increase the closer to the date. They offer AAA discounts.