As great as i think Iron Maiden is going to be, i still think you should go with whats a proven winner in MET. Pinball doesn't get any better than Metallica and even if Maiden turns out to be better, no way is it going to blow MET away, no way in hell. The other thing is MET is not being made anymore i dont think and Maiden will be available for 3 years at least. You could always sell the MET to fund the Iron Maiden pin later if you wanted to.