Mac preview question...

I often preview my RAW files by pressing space on while in OSX, but today I compared some JPG and NEF files, and there is some weird difference, NEF is more saturated and with more contrast than JPG file, Standard picture control.

Here is some sample video:

https://www.youtube.com/watch?v=J1U8zTBxc_A

Why preview in OSX reads RAW files different than LR or PS CR?

This is completely normal. NEF raw file is not an image, but unprocessed sensor data. It needs to be converted into an image (e.g. a JPG file), which requires certain algorithms and parameters, such as brightness, contrast, saturation, sharpness and so on. Depending on a choice of algorithms and parameters, you will get a different image. Internal camera converter or ViewNX2 app use different algorithms and parameters than Mac Preview. Try converting your raw files using a different converter, e.g. Adobe Camera Raw and you will get yet another different result, even if you use the same parameters as in ViewNX2, just because ACR and VNX2 use different algorithms.