both i believe
Whew... Lot's going on while I'm gone. Happy to see this thread's thriving, honestly. =)
It's a shame Meganium has literally no other point in being around, though. Even with screens up, it's set up fodder, does little damage, and at best can para-hax with Body Slam. I really recommend another screener, even if it's not some over-popular OU n00b like Blissey.
I really don't recommend set 2... Set 3 could give you a lucky break if you're (especially) facing a Hail or Sandstorm team. But, if these aren't their primary team purpose, they'l probably not lead with Hippowdon and obviously not Abomasnow; TTar is also a much less common lead nowadays, too.
Set one is, ofcourse, my favorite. However, I modify it however I please; either by giving it a Sash instead (since weather leads are, as mentioned, less common), dropping it's attack move for Protect (gives you an extra speed boost in most cases, +2 attack and speed lets you sweep pretty easily).
However, any of the sets has huge problems against today's common leads. Set 2 could counter an older metagame better, but now, with BP Metagross, the up and rising Anti-Meta Mamoswine, uncommon but possible Infernape and Weavile, perhaps a TTar or Roar Swampert in there too. And with Stealth Rock rampaging, without a spinner, Ninjask won't be coming in successfully again; aside from gettng +1 speed if it has protect, which isn't too helpful usually.
I really don't recommend Ninjask nowadays... It was overhyped in ADV (great poke, but...), and in the early days of DP.