Out of the lineup you suggest, I believe Ruger is an excellent choice. We sell a lot of them, they're not fragile, a good value, and backed by a company that stands behind it's product. I sell quite a few to guys going to the LE Academy that don't want to spend a lot on a gun for training, since they don't necessarily know what department they'll be going with, and what the dept. allows for carry.
CZ has a new double action .40 (I can't remember the model number) that we've been selling for +/- $300 that looks like a good value, but the gun is ugly compared to a CZ 75.
Taurus also has a line of .40's you might want to check in to, but I don't think they have the durability of the Ruger P series.