I only briefly used Camelot, so I cannot give a fair comparison.
There seems some overlap but also some unique points. E.g. the scripting in GigPerformer can come handy and Camelot offers a timeline to trigger instrument changes. I only use a fraction of the features of both programs though.
Best give them a try, both come with trial versions (Camelot even comes with a slimmed down free version).
You might also want to look at Mainstage or Usine Hollyhock. The first is hard to beat when it comes to included plugins (basically everything from Logic), but e.g. doesn’t support VSTs (only Audio Units), if you need this and expects all plugins of a setup to be loaded in ram all the time.
Usine is great for people who want to interact with the UI environment like with an instrument. It works well with multitouch tablet computers! It also allows to automate every possible interaction with the system with a visual, node based or scripting language (you could even create patches that create patches, like in Max or Pd). It can be a little intimidating though Have used this on Windows a lot (and stopped using it when switching to Mac for music stuff. But there is a Mac version now…)
Currently I use Gigperformer, mainly because it is not getting in the way and because I see no reason to switch The scripting feature was useful for some experiments, my current setup is script-less and as simple as it gets though. Just a list of scenes with different sounds that I switch between manually.
Wouldn’t rule out that it would be the other way around if I would have started out with Camelot