There's no doubt Amtrak is more comfortable. Even the regular Amtrak seats are better than Delta's First Class seats... except for the part where you have to spend two and a half days in them to make a trip you could fly in 8 hours. Some people enjoy the journey and some people just need to get where they're going, but air is often a quite reasonably priced way to travel compared to driving or taking the train (especially if you're used to paying for sleepers).