So, scheduling issues aside, if the Cardinal works for your dates here are my pros and cons.
Reasons to take the Cardinal:
1.The scenery. Particularly Eastbound is about the prettiest in the system.
2.Viewliner equipment. The Viewliner roomette is infinitely superior to its Superliner counterpart.
First-off, both berths are equally comfortable. On a Superliner, the upper is EXTREMELY claustrophobic, but on a Viewliner, there is plenty of headroom and even a window up there, so you won't have to fight over who gets a comfortable bed and who has to basically sleep in a coffin.
Secondly, you get an in-room toilet that you only have to share with your traveling companion. (Some people are for whatever reason more comfortable with the public restrooms on Superliners, but to me that seems like an intimacy issue if you can't poop around your family. I suppose some people are more conservative and prefer to hide their bodily functions, so if that's you, then consider this a disadvantage.) The toilet has that airplane toilet sucking action when it flushes, so I haven't ever found smell to be an issue.
3.Single Seat Ride. As you noted, the Cardinal will pick you up right in Alexandria.
Reasons to ride the Capitol Limited:
1.A shorter ride. Westbound, the Cap is basically dinner, sleep, breakfast and then you're in Chicago. Due to its long, southern route, the Cardinal comes to Alexandria at lunchtime, and still gets you to Chicago over an hour later, if it is on schedule. Because of its meandering route, however, the Cardinal is also more prone to delays. If you like train time for its own sake, maybe this is a reason to take the Cardinal.
2. The food. Since you are traveling sleeper, your meals are included in the price. Because the Cardinal lacks a full kitchen the meal selections are fewer in number and lower in quality. The Cross-Country Café on the Cap has a real kitchen downstairs, so you can get fresh eggs in the morning and steak at night. I would highly suggest visiting www.amtrakfood facts.com, where you can find pictures of the food served on various trains. That will demonstrate the abysmal quality of the offerings on the Cardinal.
3.The lounge. The beautiful views of the East panhandle of West Virginia and western Maryland on the first day on the Capitol Limited, can be enjoyed from a Sightseer Lounge, with floor to ceiling windows and great conversation. (Unlike most trains, the cafe is not downstairs, but in the same car as the diner.) Amtrak's single level lounges have only adequate windows and are just diner-style booths, rather than a "living room" setup.
4.The price. The Cardinal is almost invariably the most expensive sleeper upgrade in the entire Amtrak system. The Cap is usually the cheapest ride, not just from the DC area, but even from New York (you would have to take a regional).
For me the lower quality food on the Cardinal combined with a higher price is the deciding factor. I'm not into paying more for less. If the Cardinal ever got a real diner, I would probably be willing to pay more for the better scenery and more comfortable (to my tastes) roomette, but until then, I think the Capitol Limited is decidedly the better Alexandria to Chicago route, even if you gave to take VRE or Metro to Washington Union Station.
