It is easier for a dog to 'bust" out of a wire crate - so I prefer to use them in the conformation setting. At the training field a heavy plastic or custom Aluminium crate is my preference.
Good Info on the crates. I bought a few at Big Lots, but they had cheap light plastic pans - and broke pretty quick. Midwest are decent.
At Palm Springs 01/2005, 3 of my best wire crates were stolen - those nice spring locking, single action handle ones, with crate pads 'n covers - they knew the good stuff.