Better? Thats a very subjective word. Which one is "best" for you...thats more objective.
I prefer Mossberg, but not because it is necessarily a better gun; rather because I prefer certain features of the Mossberg (in my case the 590) vs the 870 (Im assuming you mean the Express model). As an example, the main feature which sold me on purchasing a Mossberg was the receiver mounted safety. To me, given the stressful, adrenaline pumping nature of an HD encounter, I felt that the safety location on the 590 would not require quite as much "finite" or dexterous manipulation vs. the trigger guard mounted safety of the 870. Does this make the 870 a "bad" HD weapon? Not at all. My decision was based on preference and nothing more.
Either gun will be good for HD as it should be less about the brand here and more about features. Both have strengths and weaknesses. For the Mossberg, its main weakness is the mag spring. Once this is properly replaced (with, for instance, a Wolff spring), this particular issue essentially disappears. Does this make the Mossberg junk? Not at all. Its just one of those details that, for some reason, was left unattended to by those who make the gun.
Both the Mossberg and Remington are good guns which simply have their own unique set of problems (which can be dealt with). Ive never thought of one as being "better" than the other; rather I simply think of them as "different" from one another.
Most "HD" shotguns will by Cyl. or Improved Cyl. bores w/ barrels ranging from 18" to 20." Outside of this, the rest basically boils down to what you prefer and again, which weapon "feels" best to you.
Frankly, whats going on between the ears, so to speak, has more to do with HD than the brand of shotgun you are using.
