There used to be a difference in the coatings on the two, the EL's contained a coating that was not used on the SLC's; Swarovski has since begun using identical glass on the two. The difference is the weight and the ergonomics (the feel). I went with the 10x42 SLC's and love them, but like somebody already said, it is sixes one way and half a dozen the other.
Going with Zeiss, Leica, or Swarovski is going to leave you very pleased.
(As you increase the magnification, with all glass, you decrease the amount of light allowed through, relatively speaking.)