Is the x86 Architecture Less Secure?

An anonymous reader asks: "Paul Murphy at CIO Today reports that a specific Windows buffer overflow vulnerability ' depends on the rigid stack-order execution and limited page protection inherent in the x86 architecture. If Windows ran on Risc, that vulnerability would still exist, but it would be a non-issue because the exploit opportunity would be more theoretical than practical.' And implies that other Windows vulnerabilities are actually facilitated by having an x86 chip." How does the x86 processor compare with other architectures when it comes to processor based vulnerabilities? How well have newer additions, like the Execute Disable Bit, helped in practical situations?