Understood, but I'm asking in the context of Jim's observation that 2010-2012 models offer good bang/buck, and wondering if there's a reason to
not get a 2013 if the opportunity arises. I'm told that a 2010-2012 Mac Pro would need a new video card to be able to run recent versions of OS X, for example, so that's a demerit for that model.
In other words, let's say that, hypothetically, I were in a position to be given a 2010-2012 model or a 2013 model. (Let's also say that I can't afford to buy a new Mac Pro myself; neither of those statements are really hypothetical.) Is there a reason to turn down the 2013 in favor of the earlier model?
BTW you're talking to someone who's still using a 2010 MacBook Pro (with a flaky GPU!) and running Snow Leopard most of the time.

I don't love being behind the curve, but then again given what Apple has become, I do like refusing to participate in their recent world of headphone dongles and broken promises...