I recently compared a Nikon D3200, D5200, D7100 and a D700, all using the same (or close to same) lower megapixels count of around 10. The higher end cameras made a huge difference in quality. The lower end also could not support higher end flashes.
I own a proofing company with thousands of users, and ran a print lab for years. You don't need more than 200PPI for larger prints and thus can save a lot.
In fact, considering most people order prints 11x14 and smaller, having the larger megapixels actually hurt quality because the printers (Fuji, Durst, etc.) downsample the files and you lose sharpness if you send them the large file (which most photographers do).
For my wedding shooting, I never need a larger file than 12 megapixels as that's large enough for a 30x40 at 300 dpi. I prefer to save the hard drive space.