Aluminum crates are probably going to be the best. If your not into spending that kind of money Pet porter is good.
I did go to the Rough Tough site and that seems like a real durable unit. I did like the video of them dropping 25 lb weights from 20ft above and only denting the kennel while other brands the weight went completely through or smashed the plastic. :thumbsup:
I have two Rough Toughs and they are super nice. A bit expensive though. There is a kennel manufacturer in southeast MN that is making a crate similar to the rough tough but with a better door design. I wish I could think of there name. They make welded plastic crates that are not so portable as well.