Again it all depends on what you do with your pictures, if you just use them on the web or view on a screen then obviously you don't need all the details and resolution
If you do print and especially if you sell prints then every tiny gain of quality counts.
I print hundreds of 13X18 and 15X21 photos, every now and then I print A4, and rarely A3, my largest print was 100X150 cm vinyl print from 8 megapixels 30D yet it looked fine, 20=25 MP iis all I might need, knowing sometimes I need cropping
If you do print and especially if you sell prints then every tiny gain of quality counts.
I print hundreds of 13X18 and 15X21 photos, every now and then I print A4, and rarely A3, my largest print was 100X150 cm vinyl print from 8 megapixels 30D yet it looked fine, 20=25 MP iis all I might need, knowing sometimes I need cropping