A strange comparison... E-M1 vs FF

I'm looking to get a new camera sometime towards the end of this year or the start of next one.  I had been looking very heavily at the Canon 5D Mark III, partly because I want the improved low light over my current APS-C camera.  But, as I've looked around, I keep coming back to the E-M1, which seems to match the 5D feature for feature (and then some) and the only drawback is the sensor size (but it still seems to have pretty solid low light performance up to 6400).  And, for the price of the 5D body alone I can buy the E-M1, the 12-40 2.8 and the 75 1.8 (and have some money left over).  So, i'm hoping someone on this forum has owned/used both cameras and can give me some reasons why they pick one over the other when shooting.

Largely, I shoot available light candid stuff (often indoors with poor light), but am branching out to a few other things (some sports/action and possibly product photography).  I'm pretty handy with a camera, but I'm not a pro.  I know how to use the settings and never shoot on Auto, but will freely admit that I will never max out the capability of either camera.

Thanks for the insights and info!

-W