Brent, that's what I meant by 'widest'… Actually, your post wasn't there when I wrote mine, but you pre-posted me -- so mine is really redundant. Sorry if I confused anyone.
This brings up another point:
If you're looking into getting a new shotgun, take advantage of the resources available. Download the manual for each the guns on your short list -- they will answer the standard questions (like what about shooting slugs) that we see here time after time. What these forums are best for is answers like Lavid2002's reply about loading the Mossberg. You won't find those in the owners manuals.