Upvote:3
The Church of Jesus Christ of Latter-day Saints do not have extensive doctrine on Mother in Heaven
As with many other truths of the gospel, our present knowledge about a Mother in Heaven is limited. Nevertheless, we have been given sufficient knowledge to appreciate the sacredness of this doctrine and to comprehend the divine pattern established for us as children of heavenly parents. Latter-day Saints believe that this pattern is reflected in Paul’s statement that “neither is the man without the woman, neither the woman without the man, in the Lord.” Men and women cannot be exalted without each other. Just as we have a Father in Heaven, we have a Mother in Heaven. As Elder Dallin H. Oaks of the Quorum of the Twelve Apostles has said, “Our theology begins with heavenly parents. Our highest aspiration is to be like them.”
This doctrine of family is central to God's plan for us, and can be found in the Family: A Proclamation to the World. So having this knowledge is important as it sets the goal/standard on which we (mankind) strive to attain.
In regards to the comment about polytheism see this answer.
Upvote:3
Not sure how this can be objectively answered, but these kind of doctrines certainly do make a difference, in the way that they affect ourselves and our neighbor:
The fact that LDS believe that mankind are literally children of God means that
Other than that, I'd say the Trinity and the Godhead we believe in (The Father, the Son, and the Holy Ghost as individuals but working in unison) are functionally equivalent. The Trinity, as far as I can tell, just means that somehow, somewhere behind the scene the three persons are really one God. In LDS beliefs, you also can't pray to a different person of the Godhead and expect any different result than if you had prayed to the Father, for example.