All RAW files from the same camera have the same number of pixels. I don't know of a camera that save RAW files with fewer pixels than the maximum size. The sensors in most cameras can only capture 1 single color per pixel either R, G or B. Generally there are 2 green pixels per 1 red and 1 blue. After the exposure the camera would read the analog value from each of these pixel and digitize them in either 8, 12 or 14 bit each and some cameras allow option to select this. When you convert an analog value into a digital value you divide it into some number of steps. 8 bit has 256 step, 12 bit has 4096 steps and 14 bit has 16384 steps so you can see more bits can record finer tonal gradation. If the camera use a noise reduction technique mainly for long exposure to subtract the values from a dark noise values from the image values then it can be applied to the RAW data. The RAW converter will then create 3 color values per pixels from 1 color values coming from each of the pixel using the Bayer algorithm or some other improved version.

I am going through a similar decision with an 85mm lens now...whether to get the 1.4 or the 1.8. There is a very significant price difference of $1600 vs $480, so I have asked myself if that extra ⅔ stop is worth $1200. Of course it is not, and I will get the 1.8 in a couple of days, once the Christmas presents for others are bought. I rented a 1.4 and it is very soft at 1.4. I did not try other apertures because I needed all the light that I could suck into the lens from the poor gym lighting. From the reviews that I have read, the 1.8 is sharper and faster focusing. Not sure if the same is true for the 50mm, but I would rent one of each and try them for yourself.