Ah yeah this is true now of a recent v8 update (semi-recent ish) I dont know if that applied to node v0.8 but quite possible to .10, I'll revert back but yeah it does make sense (in the same way as how Array.isArray SHOULD be quicker than instanceof Array [right now it's not but in the future v8 can internally improve array.isarray a lot better/more than instanceof). 

Thanks for pointing this out man, I literally checked a jsperf on this about 5 months ago and the results were switched. Amazing how fast shit moves :D