If I were to have only one gun, it would be a 12 guage shotgun -- by far the most versatile gun you can own. You can hunt everything from dove and squirrel with light birdshot up to deer (and probably beyond) with a slug. I wouldn't worry that much about meat damage. People have been hunting deer with slugs for decades (I live in Illinois, we can only use slug guns). Just practice, know your effective range, and only take shots that you are reasonably sure will not hit the rear quarters (a good idea with any gun, by the way). They are also ideal for waterfowl, pheasants, and turkeys. On the Mossberg, I might skip the home defense barrel, buy one with a 26 inch barrel instead of a 28 (kind of a compromise since this is an all-purpose gun), and save the money for a rifled barrel for sabot slugs if you plan on doing a lot of deer hunting (much better performance) or for a rifle of some sort -- depending on what you are interested in.
Good Luck.