Read back in this topic for many opinions, but the bottom line, literally, is how much you want to pay for more space. Most Amtrak accommodations are quite expensive these days, as there is a shortage of equipment and a surplus of people with enough money to be able to buy what they want. That's not a judgemental thing, there are many people that can afford to fly in first (or upscale business) class on airlines and do so. You didn't say in your post if there are one or two of you, which is the first but not only consideration. In the old days I've found real deals in the larger bedroom even when travelling by myself, but that's not likely today.
Take a look at the costs, and be sure to check several days before and after, as prices can vary widely. Amtrak uses a similar yield program to airplanes and cruise ships, where they set a medium price a year or so in advance and then move it up or down depending on how many sell. If you get lucky you may find a very unpopular day (Super Bowl, anyone?) and the price will be on the more reasonable side.
In terms of "value", only you can make that decision. Frankly, I can get a cheap flight somewhere and save a ton of money by not getting an Amtrak sleeping car room. I could spend that money on other aspects of my vacation or my general life. But I really enjoy riding trains, so splurge on rooms whenever possible.
I'm not sure what topic it was in, but someone posted some example "hourly" rates for a ride in a sleeping car, and it was surprisingly reasonable, around $25 or so an hour for the experience. If you really enjoy trains (or really hate flying), it will be worth it.