You should always runs Sigs wet IMHO Pay particular attention to the rails. Here is a great link and write up. This is a little less of an issue with the stainless steel framed guns but I would still run any Sig with this type of lubrication.
As far as care of a Nitron vs Stainless steel Sig it should be the same if they are current production. Stainless does not mean it cannot rust. If neglected it can and will rust....
-Fast is fine, but accurate is final. The trick is learning to take your time when you're in a hurry." -Wyatt Earp
-Its a tool box... I don't care you put the tools in for the job that's all... -Sam from Ronin
-It is the mark of an educated mind to be able to entertain a thought without accepting it. -Aristotle
-Without deviation from the norm, progress is not possible.-Frank Zappa