More options for hydro-dynamic hull designs and interior layout, less kiting in a breeze, quieter while fishing (no hull slap), more stable overall (because of its weight), you don't have to have high deep V style gunnels in rough water, no welds to break or rivets to leak, and they are prettier.
Aluminum rigs are better in the ultra-shallows, easier to tow, require less horsepower on the back and less powerful trolling motors on the front.