and the only thing better about an 870 then a Mossberg is the name.
Get the one that fits you, both are quality weapons and will last you a life time. MB are a little less expensive then Remington but will work as long as you want it too.
I have a MB500A, great gun, never fails to fire. My friend has an 870, coated with rust within the first month, only holds 5 rounds and jams on him. Could be lemon b/c I know he takes care of his weapons but you never know.
Play with them both at the store and see what you like, both are quality firearms.