The E version stands for Enthusiast, it is supposed to be more powerful than the non E versions in the same generation.
So the i7-3820 is the better version. Even more so that it is cheaper.
But... Is that E overclockable? If it's not, maybe it's not better. Sandy Bridge-k can over-clock well to even higher performance.
I'm not sure if E without the K can overclock. But if you don't want to overclock then the E would be better. (unless it can overclock like the i7-2700k then it is definitely better)