I'll second George: What are you going to do with it?
If you are going to camp or fish, take the HK: Durable finish, rugged, easy to opperate controls, accurate as hell. FWIW, so long as your hands are big enough, I would take a fullsize as it has the two spring recoil reduction system instead of just one spring and a plastic bushing.
If you are just going to target shoot it or use it for home defense, take the SIG: finely machined, sweet trigger, nice piece of machinery to own. I think I would go with the 229 onm this one as it is in production and I have heard good things about the slide... Dont know for sure, but I thought that the P226 had a folded metal pinned block slide instead of a milled slide.
I did a lot of testing at the range between SIG and HK before I bought my USP45fullsize and pretty much thought the same thing everyone else has here.
The Steyr? Dont know anything about it! :]
J.T.
As always, FWIW,IMHO, YMMV, and all that