PowerPC processors are just that little bit harder to produce exploits on than x86 processors. You have to do a LOT of legwork that x86 does for you.
There are some nice articles about this on the internet by a guy named Chris Shepherd. It's all very technical and all very true.
http://www.belgo.org/propeller/ppc-stack-1.htmlAssuming that it is this Chris Shephard that you mean, and after having read the three articles I can't really see that there is that much to it. Offcourse there are improvements over plain x86, but nothing that will stop a competent attacker. So IMHO using PowerPC over x86 is just security through obscurity, and nothing more.
