They all do the same thing, but I don't think that captures the truth. Here are some interviews with the developers themselves. They all seem excited for and happy about perl6. And I also want to say for the record that I think all the frameworks are great, just that Mojo is greater. The way it starts out with a one page app and then grows, support for testing, model agnostic, javascript agnostic, template helpers, asset packs that support things like JS combining and minification, it feels like SRI knew your pains and went out of his way to make your life better.

Catalyst I felt like starts out huge and forces a great, hard learned, best practicey and mature SW Engineering Philosophy on you. Who wants that baggage? Not me. I did use Dancer, and I even found my old node where that was my opinion: Re: Pro/Cons Catalyst/Mojolicous/Dancer. But, my opinion changed, mostly because when your apps get larger, in Dancer they have nowhere to go. Plus Dancer2 came out and it is like.. what is going on here. Without Catalyst there would be no Mojolicious and they all are better than what came before.