its all about what you're trying to do.
if you have a small show with one or two outputs then Qlab is fine.

As far as I can see Qlab 3 still can't do keystoneing on a global level, or curved screens, or alot of the things we take for granted in Catalyst.

The other major way Qlab falls down is when you need to use more than one server. Multiple Catalyst servers can be controlled centrally from one console... Qlab cant.