I think I'm the only one who went to both the Tyler and the Williams and was also in the two 'afterparties'. I can't remember meeting anyone at the Williams afterparty that was also at the Tyler afterparty, anyway.
My group of 4 went to both. Unfortunately, I did not have any connections to 'afterparties' in London. I think both concerts were as expected. I liked the Tyler one as well, my expectations were met. Both concerts are not comparable IMHO.