1. Hacker finds Security Hole
2. Hacker exploits Security Hole
3. Microsoft finds way to detect exploit
4. Microsoft bans exploited systems
5. Hacker finds new Security Hole that isnt detected by Microsoft
6. Hacker exploits Security Hole
7. Microsoft finds way to detect exploit
8. Microsoft bans exploited systems
9. GOTO 5

With Sony vs hacked PSPs, if a security hole is found a PSP can be reverted to exactly what it was like before, not the case with a banned Xbox360.

In the end, unless a 100% undetectable exploit is found, which is unlikely, MS is winning because the banned systems can never get back on Live. Until the day a hack is found that somehow allows a banned system back in MS is in the lead with this.