cybersansar.com : Students
dcnepal.com : Housewives, Cheap entertainment seekersmysansar.com : Mixed (almost everybody) except those born in USA
nepalnews.com: mixed but with the rise of nepali language sites (nagariknews, mysansar & kantipur) their market share might be going south. But foreigners may rely on them
sajha.com: Students (age: 18-25), Professionals (age: 22-40)
If you want to bring google adsense money, use dcnepal & mysansar
If you want to sell products & services use Sajha & nagariknews together
If you will be in entertainment business use cybersansar but your visitors expect same materials as CS
If your target group is kids :) born here (nepali) use Facebook, they don't care about all these craps
Make your own decision.