Walther!
Out of the three you mentioned, I would pick none. Whatever you do don't get the Smith. I have heard of some serious problems coming from I think Maryland State Police, or maybit was Massachusetts. Anyway, they have had lots of malfunctions, and failures to fire. I do have experience with the Walther P99, and it is absolutely fabulous. I would go with it first off.
If you are not willing to get a Walther, get a Sig. I personally recommend the P229, not a Sig pro. If you think this is too big, that is fine, but I would still get something similar like the p226. Just my little contribution.