I just bought one with green circle dot and I also bought a Holosun 507c with green circle dot. The swampfox is very high quality but doesn't have the bells and whistles of the Holosun. The 65 MOA circle on the kingslayer seems clearer than the 32 MOA circle on the Holosun. Overall it's excellent and you won't go wrong getting one.
Edit - I realized this morning that you have to be careful when attaching the sight to the base - you need to watch how much you tighten it down. I had to barely tighten it otherwise it will not turn on. I was using a Wheeler fat wrench set to 15/in lbs. It was set based on the Holosun specs. It's kind of finicky that way and I would definitely add blue thread locker to this one but I think I'm keeping the Holosun although the $187 difference is a big pill to swallow.