thats questionable. pl u21 xi:
lukaku
sterling kane oxlade
can barkley
shaw stones chambers bellerin
i doubt any league could come up with a much better u21 side.
what i would say is that la liga (and some other european leagues) play a more technical brand of football than the pl. and if this is what you want to see, then on this basis, la liga may be the best league for you. but i dont think necessarily means that la liga players are technically better than pl players either. its more of a stylistic thing. and i think often people make a mistake here thinking that la liga players are automatically technically more gifted (as a whole).
im with galeforce here. for me the best league is a mix of things, but ultimately its about what the highest number of people want to watch and give the most money to. and on this basis, this is a non-debate.