Spent a couple of months carrying around three pairs of binoculars. Before that spent three months reading birdwatching articles about the EL V. SLC debate.
Here is what I think is the right explanation. I have heard many others, but I think this is correct.
Feel --- the two models have a different feel in your hands. The distance between the eye objectives on the SLC was greater than the EL. This is not an issue for most people but it is for some.
Weight --- One weights more than the other.
Lense coating --- The EL's and SLC's have a different coating applied to their respective lenses. The SLC's has a warmer tone (orange and red) application and the EL's have a cooler tone (blue and green)application. When you look for it you can see the difference. The difference shows up the most when you have a natural white (snow) next to a natural black (dirt or rock) under neutral light. The best way I can describe the difference is the color shift during a dramatic sunset. The cooler colors take on a warmer color tone. The difference between the EL's and SLC's is not that dramatic but you can see it. Doesn't effect clarity, magnification, light gathering, or function, but the cooler tones do give you a more realistic image, or at least closer to what you see without the glasses. At least to my eyes.
From my perspective the EL's and the cooler tones gave me a slightly (very slightly) crisper and clearer image.
My plan was to sell the two pairs of binoculars I didn't select. I went with the 8.5 X 42 EL's and sold the others.