They are both good in their own ways.
I just get tired of recommending the DS3, P5B-E, and P5B Deluxe. I think we all do lol.
The P6N is the 650i chipset which has shown to be a very good chipset. For extreme overclocking the DS3 probably is better since it's a 965 chipset which loves high FSB. Still The MSI P6N is only 118 bucks and is very nice with SLI as well.
Like I said the DS3 is still a good board but I'm tired of it i have recommended it over 100 times probably and the 650i chipset is newer and more "IN"
Can't go wrong with either though really.