Philipoussis is just a big server, because he's a dumb server, a macho server. He's a stiff server, with a stiff motion, and he doesn't get as much spin out of his serve as he could as a result. The result is a shotgun serve, a bullet up the t, out wide, or right at you...but always still a bullet. Yes, he can hit with spin too, but it's not like he can swing it out WAY wide like Goran can on the slice, or kick it out way wide like Sampras, Roddick, and Rafter can. Philipoussis is a limited server, and I think the most overrated server.
His serve is intimidating and nets him many aces and easy holds, but he can't count on it when he gets tight and in the most important of situations I feel as reliably as he could or should. This is, because his motion is made to smack the ball flat, but not for spin. When he gets tight, he goes for big flat serves, even on the second serve. I've seen so many huge double faults from him through the years, which really proves that you live by the sword, you die by the sword.
I don't soley believe that this trigger mentality on the second serve in pivotal moments is just because he's got an agressive mentality as he likes to say. I think it's because it's a mental cop-out, because he doesn't have as much faith in his second serve as he should. IF he could generate AGRESSIVE spin on his second serve the way Roddick and Sampras could, I don't think you'd see him going for foolhardy, roll the dice, take my chances, all or nothing, hail mary, flat as a pancake, sling shot, bullet, catapult away, second serves. You get the point.