Well, at least people who wanted LA knew the potential quality from seeing the many snippets of it and the clips from The One. So they were requesting something which they saw and knew could look potentially look great on an official release. Those who wanted Wembley didn't see HQ clips of the concert and wanted it just because they heard a few people saying he was good during that night (which might as well be true, but if the quality sucks, what's the point in releasing it?).
'We want LA because there are a lot of clips and snippets from it, and they look great!"
"We want Wembley because somebody told us he was great during that night..."
...yeah.