i'd go with the .45. i'm not that big a fan of Sigs because i don't paticularly like DA pistols. i have nothing against them though and i feel they are very reliable, accurate, well made pistols. the 220 also feels better in my hands than the 226.
i don't like the .40 as much as the .45 or 9mm because i don't feel it's balistics are any better and it recoils more. i can place several 9mm rounds on a target quickly and accurately which has more stopping power than a single round of .40.
in .45 for home defense i'd go with either a Glock 21 or any well made, reliable 1911 such as a Kimber. in .40 i'd take a Glock 22 and in 9mm i'd go with a Glock 19 (which is my current home defense pistol).