It's pretty subjective, but my personal impression is that it's pretty decent in low light. We have a few different brands of cameras set up in pretty pitiful light in QA, and -without naming names - I'd say it looks every bit as good as a significantly more expensive 'big brand name' camera.
I know that exist a few more brands introducing 4k PTZ cams in last months. According with this, in my opinion, It's a disadvantage buy a 1080p cam this days... Sorry, my ittention is to make a constructive dialogue.
I'm all for a 4k NDI cam, and I'll be happy if we're the first to do it. But at this time, no one has announced one...including us. There's still plenty of demand for 1080i, much less 1080/60p (which is probably more important than 4k right now to many).