IMHO it's too early for that question, as no one(!) has actually enough practical experience with Perl6 to be able to make such a statement.
If someone does (make such a statement), it's just because of his wishes/estimates/feelings/half-knowledge/advocacy of this not-yet-released-thus-hypothetical-future language.
I can tell you what the current estimate/feeling is here at our R&D:
- We do not yet care about Perl6, as there is no release date and Perl5 delivers what we need.
- Our concensus is, that Perl6 development does take too long and we don't think this will necessarily mean the resulting language will be better. Actually many projects who do not have "self-imposed" deadlines, tend to be ... well ... mediocre. (I'm not telling projects which are released way before they are ready just because of a deadline are any better - it's as always somewhere in between where truth lies)
- At the time, when Perl6 will have been officially released for some months, we will take a peek and probably do some small-scale internal projects with it. Maybe even "upgrade" some Perl5 stuff to Perl6 if it looks promising.
Only after that, I believe, developers who have participated on these projects involving Perl6 will have the chance to be able to come up with a short, clean and compelling reason for "Why Perl6". That is - only if Perl6 will also deliver like it's ancestor.