in what sense is what's happening to Greece now significantly better economically than what happened to Weimar Germany?

It's not, of course.  

During the middle years of the Weimar Republic Germany experienced a burst of "prosperity" based on capital inflows (debt accumulation.)  This inflow was used for current account purposes instead of being deployed as long term capital to increase productive capacity  -- & is this beginning to sound familiar?  

:-)

It's the same old story: the inability to cognize the fundamental difference between "wealth" and "accumulating stuff."

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre