I've played both. I'm only a 1600 level player in LoL after nearly 6 months of playing whereas I was a grandmaster in SC2 for multiple seasons. NA and EU although I played sc2 for nearly a year.
LoL is a different genre of game than sc2 and they really cant be compared. (yes I know I just compared them a little)
if people practice LoL just as hard as they practice SC2 or BW it would be just as difficult and high level. Remember how people used to say SC2 competition was a farce? Well yeah it was the first few seasons, LoL is in it's first few seasons as well.