The two frameworks fill different needs. Rails might be great for a completely new product, where you can fully take advantage of its "Convention over Configuration" motto as well as its neat integration between M, V, and C.
Catalyst aims to be an extensible framework. Sure, there are recommendations for new projects, such as using DBIx::Class as the ORM, or Template Toolkit for your view, but these aren't written in stone. Each layer is flexible. You can use CPAN modules to build your own models and views. Want world GDP data? Make a model that calls WebService::CIA. Have your own custom database model already? Use it! (SixApart did this with Catalyst their partitioned database system Memcached).
Catalyst is a little rough around the edges for some of the simpler cases that you might use RoR for, such as a plain old CRUD form system, which Rails will nicely generate for you, but for more complex applications Catalyst is not a bad choice.
I love Catalyst.
