You are looking at cameras that are not on the ideal MP/sensor ratio and appear to be chasing MP.
If low light is a requirement, then you want MP/sensor ratios in green below:
The biggest advantage the 7 series has is more analytics like parking and ANPR, which if you don't need it, why spend it.
You also mentioned you want full color night vision capabilities.
Don't be sold by the marketing hype. It is not all it is cracked up to be.
I have said this before in the forum, but it is worth repeating. Do not be sold by some trademarked night color vision (Full Color, ColorVu, Starlight, etc.) that is a marketing ploy in a lot of ways lol. It is simply what a manufacturer wants to claim for low-light performance, but there are so many games that can be played even with the how they report the Lux numbers. They will claim a low lux of 0.0005 for example, but then that is with a wide open iris and a shutter at 1/3 second and an f1.0 - as soon as you have motion in it, it will be crap. You need a shutter of at minimum 1/60 second to reduce a lot of blur from someone walking.
All cameras need light regardless of what any marketing claims. You cannot defy the law of physics. I can make a crap camera look like noon at midnight, but then motion is a blur.
Sensor size, F number, MP, quality of the lens and sensor and software running the cameras are the real determining factors. And then obviously dial each cameras specific software settings to optimize the image and video. A brightness of 50 for example will look different between two different brands, or even the same brand but different cameras.
It is interesting how many of us experience better camera images with the camera LED off, regardless of whether it is a Hik or Dahua! I personally don't think they cast a far enough light to be effective. They are blinding looking at the camera, but do not project enough light out far enough to be effective. I have 3 different cameras with the LED and I do not run any of them on!
Unless you know you have enough ambient light or can live with the camera's white LED on, go with a camera that can see infrared. The full color type cameras cannot see infrared, so you couldn't add external IR later. You can always run a camera with infrared in force color if you have the available light.
But in a completely black situation without any ambient light and without the white LED on, it looks like crap and you cannot add external IR as it won't see it.
I have a Full Color type camera and the LED light on it is a gimmick. It helps for a small diameter circle, but it is no different than going outside at pitch black and turning on your cell phone light - it is bright looking directly at the LED light, but it doesn't spread out and reach very far. Fortunately I have enough ambient light that I do not need the little piddly LED light on and it actually looks worse with it on, but it performs better than my other cameras when tested at the same location. But without some light, a camera with IR capability is the safer bet.
