Would you say that wing chun is more or less useful than PTK as a knife defense method?
Which knives? WC does pretty well with the BCD. The problem is that training is held back so long, it's hard to build real competence. For that reason alone, I favor Eskrima. And within FMA, PTK is especially blade oriented. By contrast, the WC most of us train in primarily hand to hand, not hand to blade.