Actually, it all depends on the species. Each has it's own specific use: for eg, you can't use solid hardwood in a basement only above grade. You can use engineered in either, basements or above grade.
Engineered is actually a thin layer of hardwood applied to a manmade base (ie: plywood).
Hardwood can be refinished numerous times, most engineered can only be done once. Because of the ply base, engineered dents quite easily, hardwood such as maple or oak, not so much.