50L vs 24-70LII

I'm interested in anyone who has both or used both. My major specifc use would be for outdoor portraits (need something wider than 70-200 at times), for use on 5DII. It appears from some reports, 24-70 at 50mm rivals sharpness of 50L. For those having used both, do you feel the larger aperture of the 50 and much lower price more than offset the versatility of the zoom?