Except for the proven track record of centrally planned nations having much better standards of living and faster growth than more "free market" nations (See: China, Sweden, Japan, India, almost any pre-revolution socialist Latin American country, etc.).
Are you kidding? China has "much better standards of living"? Better then where? Somali? (not to mention China is hardly socialist economically)
Sweden and the likes: in short term maybe (and at what cost?) but in long term highly unlikely. Their "standard of living" exists[ed?] just for a few decades which is nothing historically.
Check out this article for example:
http://www.brusselsjournal.com/node/510BTW, Greece is ruled by socialists and has a rather socialist economy. Look where it got them.