Well, to be honest, I don't mess with too many Nissans in my area but generally speaking, OEM alarms usualy suck. Case in point, had a guy wanting to beef up his Escalade since he put about 10k worth of stereo/video. So, I sold him a Python 900 with remote start
www.directed.com It's directed's best alarm to date. I also put upgrades like motion, hood, and tilt sensors. He also bought directed's tracking system. He went to Florida to watch the spring training. Went inside to the ballpark then when he came back, his ride was gone. Onstar said they show it still being right where he parked it. 4hours later the cops tagged the thieves going down the highway 250 miles away. The theif was dumbfounded that they caught him. He had already had new plates on the vehicle. The truck had Onstar plus GM's Passkey system which they easily got passed. We don't know if the alarm ever went off because the 2way remote never sounded.
Talking just alarms, I like Compustar units better
www.compustar.org They pretty much put the 2way technology on the map. Their top unit can give up to 2mile real world range. DEI's stuff isn't bad either but I don't like the range on their remotes. I had the Python 900 on my car and one day went to Subway to eat. I wasn't more than about 50-75' away and the alarm went off because of kids messing with my car. My remote never responded.