This tendentious George Will column (via Memeorandum) has its good points, but this is a dumb question: "Why, exactly, would it be less “divisive” for the court to uphold the
broadly disliked Obamacare 5 to 4 than to overturn it 5 to 4?"
The relatively easy answer that upholding by a 5 to 4 vote maintains the status quo and allows the political branches to decide the issue—if Obamacare is as unpopular as Wills believes it to be, then President Romney and a Republican Congress will have an opportunity to repeal it next year. My guess is that Wills is afraid the either Romney won't win, or even worse, he'll win but the Republicans will fail to repeal.
If, on the other hand, the Court overturns Obamacare, it will be injecting itself into a hotly contested election in an unseemly fashion.