I've done a cache on terracaching and one on navicaching, and a munzee, and I'm a member of opencaching too. Oh and there are a couple of sites which are individuals cache pages that I occasionally have a nosey at.
But 99% of my day to day cache related surfing is gc.com. Think I'd visit the others if there were more than a scattering of caches in Scotland, and if they did events.
Not being the most technical, it was 7 years before I dared try GSAK, I'm kinda entrenched with gc.com as I can use it. Now I have a decent mobile then munzees are now doable for me too.
I'm all for the other listing sites, I just don't always understand them
Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better. - Samuel Beckett