Just want to add in. I don't think Tamiya can make such a clumsy mistake (ie. mistakenly put the aluminium center pulley in 414M2). But if they do, you are the lucky ones then. I have seen a lot of 414M2 at my local track and none came with the aluminium center pulley (ie. the teeth). Unless, you are speaking about the item where the pulley sits (ie. the center one way housing).
Anyway, the opinion I gave earlier was just based on my personal experience with ALL 3 models that I have and race them, ie. 414M, 414M2 and 414M WRC. Thus, I can assure you, that there is no bias opinion towards certain model here.
You may also check with your LHS, if you buy the shock separately, the price of the silver shock is more expensive than the blue ones. It shows the different in quality. Logically, the blue anodized should be more expensive, right? (because of the anodizing and stuff). But it doesn't. The same logic is applied to the bearings. After I raced both 414M and the 414M2.... the blue shield bearing actually is much smoother.
Anyway, I love all of them, with all their plus and minuses. So, I hope no one get offended with my opinion. Again, it was just my opinion based on my personal experience with all those great models.