A lot of people use these kinds of playpens. Just be aware to never leave your pet unsupervised and consider the possibility that a chinchilla can jump over it if it's determined enough. A chinchilla can jump 5-6 feet. Having playtime and out of cage exercise time is nice to watch but be very careful of overheating. I recommend 15 minutes or less per session.
Although I have not used these it appears the Ware is the better of the two, since it's 29" inches tall vs 15" tall. So the Midwest pen I think is going to be inadequate. Also there is a review there from a chinchilla owner who seems to be happy with it.