Yes, there is a big difference between hiding and softening. In your case (unless you have some very special reason), I would not hide but soften.
Hiding will leave those (small, seemingly rectangular but probably triangulated) facets separate and your mesh will remain faceted. These facets can be selected individually even with hidden geometry (View menu) off.
If you soften the dividing edges however, the whole surface will be one, continuous and (seemingly) nicely curved surface. Now the whole mesh can be selected as a whole unless you turn on hidden geometry.