BlayGlock:
The heavier bullets are, IMO, necessary in scenarios in which you're likely to encounter intermediate barriers. Such barriers can include any number of things like wood of various densities, metal, auto glass, but especially in the colder weather (or if you live in areas of the U.S. where the winter season is long) various clothing material that is bulky, layered or densely constructed, or that consists of heavy denim and leather. Such material can slow or deflect a projectile or cause premature expansion, thereby inhibiting deep penetration to vital organs. Even overly large metal belt-buckles have been known to stop or deflect certain bullet-styles in certain calibers ...
True, the 10mm is versatile enough - with its huge array of bullet-styles and weights - that you can find a dedicated "woods load" for back-up while hunting, but don't get sucked into believing the heavier 10mm loads are only good for "hunting/woods" use and the lighter ones for SD, EDC, or duty use. The classic "heavy & fast" 180gn, 190gn and 200gn loads (with the right HP bullet) are suitable for defensive uses too.
Also, as someone pointed out, McNett @ DT makes what is essentially a "designer" low-penetrating SD/HD load using the incredibly destructive 135gn Nosler JHP @ 1600fps/768fpe. This load was specifically created for users who wanted the least amount of penetration for, e.g., EDC in crowded urban areas, SD inside a thin-walled apartment, etc.