Henderson hasn't done anything lately other than beating Misaki in early 06 (Which Misaki avenged later on). He's far from the number 2 MW.
I'd pick Rich Franklin to be number 2. He holds wins over guys like Lutter, Okami and MacDonald and has been beaten by the number 1 guy twice.
However, if Rich is moving up to 205 for good, then I'd say Filho.