Glad that you know the differences in 8 vs 16-bit because if you are going to use ProPhoto RGB, you'll need to work on 16-bit images to avoid potential banding...
The advantages of ProPhoto RGB is that it's the only color space that can contain all the colors your image can capture in raw and all the colors that todays wide gamut printers can print (ignoring CMYK for the moment). Both sRGB and Adobe RGB will clip colors your camera can capture and once clipped, they can not be added back...
I encourage you to test ProPhoto RGB with some caveats…first off, no display can actually show the full gamut of PP RGB…the wide gamut displays can only approach about 98% of Adobe RGB so when working, you need need to be sensitive to the fact that some colors in PP RGB will not be visible on your display…and that leads to the second caveat, that you are working on a calibrated and profiled display…are you?
The areas where PP RGB will contain more colors than Adobe RGB are in strong reds, oranges, greens & blues…if you images don't obtain those colors, you may well not see any actually differences in normal output…but test it out and get back to us...