I think it depends on the university you're applying to.
Some universities see that doing an EE in science or maths (which is obviously very challenging) reflects that the student is a risk taker and is willing to carry out a real scientific research. And accordingly, they don't pay much attention to whether you got an A or not (but I'm not saying go and get a D!). These universities see that "IB is all about taking risks and challenging yourself", and if u choose a "relatively" easy subject, they'll take it as if you've just chosen the easier way to get more points.
Other universities don't pay much attention to the topic of your extended essay and just count your points in IB.
I don't know much about how UK universities evaluate it honestly. But I'd say if you already have a college list, start contacting some admission officers from those universities and ask about how they evaluate the EE.