Either Mossberg or Remington will have the accessories you want available.
At the lower end I think Mossberg definitely has an edge. I wouldn't buy one of the lower end Remingtons.
Using one shotgun with different barrels doesn't work as well as you might think.
If you want to use for deer hunting and SD then I recommend you look at just leaving a rifled barrel in all the time. Enlarges the buckshot pattern significantly and are usually about 18 inches.