Smith can pull off the badass bit, and I actually prefer his style more than Tennant's since I find Tennant's acting to be a bit too loud.

I just think the stonehenge bit didn't have the same badass aura because it's been set up a few scenes back that the doctor thinks they have no chance against all the warships. We (the viewers) know that he's just bluffing.

Compared to his line at the library, or his warning for the Atraxis - he was threatening them.