I recently came across a video by a Trinitarian apologist (Robert Bowman) who made this following claim:
I'd love to get, you know, one representative of each of these groups in a room together, sometime, and just let them fight it out, you know, because what they do is, they constantly attack the doctrine of the Trinity, but they rarely talk about each other. Jehovah's Witnesses, they have, once in a blue moon, they talk about the Mormons, and vice versa and even that is rarer, they generally don't talk about each others' anti-Trinitarian heresies; they spend most of their time attacking the Nicene Creed, Orthodox Christianity. (beginning at the 12:20 mark)
Now, it is true that LDS tend to focus on the Trinity as opposed to other non-Trinitarian expressions of theology, but that is due to the issue of numbers—there are more Trinitarians than there are Christadelphians and other modern Socinians, for example.
Notwithstanding, while some may be guilty of focusing only on the Trinity to the exclusion of other aberrant expressions of Christology and other fields, that is not the case for many LDS apologists, myself included, who have critiqued non-Trinitarian Christologies. For instance, here are posts on my blog critiquing such theologies:
Jehovah's Witnesses (form of Arianism):
Modalism:
Christadelphians and other modern Socinians (e.g., Anthony Buzzard):
Jesus was not a Unitarian (leads to a full review by David Paulsen et al. of Anthony Buzzard, Jesus was not a Trinitarian: A Call to Return to the Creed of Jesus [2007])
Did Jesus offer a sacrifice for Himself? (some Christadelphians hold to this!)
Critique of the Christadelphian view on Satan and Demons
Much of the Christadelphian view on the "number" of God (Unitary monotheism) and their rejection of the personal pre-existence of Jesus over a merely notional pre-existence is informed, in part, by their view on Satan and Demons (they reject the ontological existence of supernatural evil as they view such an affront to the sovereignty of God). Here are some articles on this issue:
With respect to the following comment:
I'd love to get, you know, one representative of each of these groups in a room together, sometime, and just let them fight it out
If he would like to ever moderate a debate between myself and a proponent of these theologies (e.g., Anthony Buzzard on the personal pre-existence of Jesus), I am game.