Granted, the big boy studios have spent zillions on the vocal booth's acoustic treatment to reduce the boxiness found in a vocal booth. This usually makes them okay. Of course, I've spoke with plenty of engineers who work in pro studios everyday who HATE the sound of vocal booths. So just keep in mind that vocal booths have a sound. It's up to you to decide if that sound fits the vocal sound you are going for in a project.
Also remember, that vocals are often heavily compressed. Compression will suck the room into the microphone. If you are tracking vocals in the right room, this can be a great thing. If you are tracking vocals in a not so great room, this is a horrible thing! The sound of your vocal booth will be much more obvious when you crank up the compression.
So keep in mind that it's extremely important to properly treat a vocal booth acoustically. If you don't believe me, pull out your clothes and try tracking some vocals in your closet. I'd be surprised if you like the sound! Simply putting a singer into some tiny, untreated room will be a disaster. Do not do it!!