Nothing against the Colt, but if it were me, I'd opt for the 686. For that matter, I did! Colts are nice guns, all right, but for the long haul I'd still get the Smith.
BTW -- 686's are stainless, not nickeled.
Also -- shop around for that 4" 686. I got mine used back last November for $300 in really good condition, that price you are quoting sounds an awful lot like NIB retail to me.