Both diffs are great options and will work well for what you need. From out experience the Nismo will be the quieter of the two, if that matters to you. Like a couple others have said, changing your fluid will help keep some noise down and will definitely extended the life of your diff.
We have built several LSx swap 240's and used a Tomei 2way in all of them but one were the customer requested OS Giken. All those cars including our own Tra-Kyoto coupe have had zero problems with the Tomei's. Just another option to think about, plus they are typically cheaper.
Short Video of our car at a near by drift day.
DD33 MWC - Tandem Final - Drift day 33 Midwest cup - YouTube
Another video of our car using the same diff but for roadracing.
Blackhawk Farms Raceway - LS1 240SX chasing 72 Vette - YouTube