I have two crates. When traveling in the car, I use a plastic crate. My dog is small, so it's easy to carry in and out with her in it. I like this option for travel because I take my dog to family get togethers. When we eat, I can lock her in her crate so she isn't bugging everyone.
She still sleeps in a crate. For this, I have a wire crate. It has enough room for her bed and her blanket. She can sit up and move around easily. She gets enough ventilation, even though she prefers sleeping under the blankets. The only problem is it's heavy. At least, it's too heavy for me to move around.