First, islam isn't claiming to be a complete restoration of Christianity like mormonism. Mormonism claims that ALL of Christianity was lost, that we're all apostates, Whores of Babylon, that Christ lied.
They claim that God and Jesus visited JS in a secret grove claiming all of this and more. Again, claiming that God lied when He said that upon His return, the WHOLE world would know, He wouldn't meet in secret with some 15 or whatever year old conman and thief.
Second, islam is known for what it is, mormonism otoh has done a very fine job of disguising just what it's really all about. That one's salvation has to be EARNED, but one never will truly know it it's been earned because they have to do all of this "work" and then hope that when they get to heaven, the mormon christ will decide to "pay off any balance owed".
Third, islam at least, minimally recognizes the divinity of Christ, where mormonism otoh, relegates Christ to just another man, who was conceived through physical relations.
Fourth, the mormon christ, upon his resurrection, is a murderous savage, not a loving redeemer. He's an OT style judge, slaughtering millions of people and destroying around 16 cities. See:
Lastly, mormonism deceives its followers into minimizing the saving grace of Christ. They teach and perform pagan rituals in their temples, claiming that without those rituals, there is no exaltation. Without exaltation, there is no dwelling in the presence of the mormon god and no chance to become a god themselves to rule over their planet, engaged in eternal, celestial polygamous sex in order to populate said planet.
Sorry, but mormonism is a problem, it's a problem for any right believing Christian who sees the danger posed to one's soul by mormonism. The teachings and doctrines are insidiously hidden, to deceive. Islam is what it is, any fool who becomes a muslim knows exactly what they're getting into. Mormonism is a "milk before meat" religion, hides most of the unpalatable aspects until one is firmly committed.
Excellent point.