I love the 500 combo and would buy it again without thought. (Compared to the Rem 870, both the location of the safety and slide release are both enough reason to go with the 500, for me. The lower cost of the 500 compared to the 870 just sweetens the dear further.)
If you have any inclination that you may hunt with your new shotgun...regardless of the game (with different loads you can hunt, bird, rabbit, deer and larger, all with this shotgun) , then I would highly recommend going with a combo that includes a shorter barrel for home defense and also a longer barrel for bird, or even clays.
Or, if you see a combo that includes a barrel between 22-24" that has rifle sights on it, I would definitely recommend that too, since that will increase your accuracy/capabilities when hunting.