I prefer headcrabs. They chomp on you, you run and scream a bit, then die. Simply and fast. When you been faceraped, you pass unconscious, then wake up and half-hour later found yourself with little alien sticking out of your chest. And this is also extremely painful, BTW.
On the other hand, headcrab zombies are still alive, even as a hostile alien parasite has burrowed into their brain and is controlling their movements, but leaving them with enough awareness of their situation and control over their voice to plead for death (Albeit in backwards speech). There's a reason headcrab zombies scream when you set them on fire. Facehugger for sure.