I'm not a fan of rails on my carry guns so my p220 sas carry works well for me.
However, if you are looking for a p220 that conceals better I'd look at picking up a p220 sas compact. The shorter frame will make a bigger difference in concealment IMO.
http://www.gunbroker.com/item/649908830
I will ditto this. While my EDC P320 has the rail, none of my current metal frame Sig's have rails and I prefer them that way. I have a P227 SAS that is really nice. The extra rounds and the melt make it a nice carry gun when I am so inclined.
This is totally my opinion (that means it and $4 will get you coffee at StarBucks); I have had multiple full size P series guns and they all feel like too much for a EDC.
Now I am a big man, 6'6", so I can CCW my KSG if I really wanted to, but to me, the full size P series guns are best suited to OWB CCW. Even my P320 Compact versions tend to get into my back pocket making getting to my wallet a chore. That and for what you are getting it for; and to me the key tenant to a good CCW is this; for what you will be using it for do you really need the extra length and weight?
Now, if you want a bed side gun, go for it. The longer sight radius "might" be a factor if you have a huge house. I tend to use compact or carry guns here as well as I want something my wife is comfortable holding and using.
So ultimately you have to decide for yourself. Just be practice. Regardless, the key to carrying larger guns is a really good holster.
Good Luck!