Well alot of people will tell you 12 guage <img src=icon_smile_big.gif border=0 align=middle> and that is a great weapon. BUT since you asked about pistols....
The .357 magnum is a good home defense round. A great advantage is that you can load it with .38spcl's to help reduce muzzle flash, recoil and going through your house and killing an innocent. Of course frangable ammo can be obtained for both the .357mag and .38spcl which would aid in the innocent part. I would opt for at least a 4" barrel for home defense. The short barrels, 2" -3" have considerable more muzzle flash then the longer 4" - 6". I also prefer the feel of a 4" S&W 19 or Ruger GP 100.
The .357 sig is a great round in it's own right. It was devolped by Sig Sauer to replace the .357mag 125 grain round for a semi-auto pistol. I'm actually a pretty big fan and like them in the Glock 32. HOWEVER the .357sig will not work in a .357mag revolver. The .357sig round is a .40S&W round bottle necked down to hold a 9mm bullet. It's basically a 9mm +P+.
Hope the info helps.
"A vote is like a rifle: its usefulness depends upon the character of the user."
Theodore Roosevelt
http://tscott.fws1.com
ONE NATION UNDER GOD!