These are not rhetorical questions.
I think you would have to look at the literal textbook definition of what makes a cult to understand why the two are considered Cults. Walter Martin sums up pretty well in Kingdom of the Cults which has been a mainstay resource on cultism for years. Martin in his lifetime was the foremost expert on comparative religion studies. Very well studied to the point that practically every group he studied and reported on accused him of being an apostate from their group because he "knew too much not to be."
With regard to what pretends at Christianity, we would label them to be false or pseudo-adherents - much like the Jonestown group from which we get the modern phrase "don't drink the koolaid".
Denominations vary from the harmless to the wildly absurd. The thing that differentiates them largely is what they follow, obviously. When they diverge from Scripture and become doctrinally in contention with scripture, especially on core issues, the status of cult is pretty much a gimme. There is one prominant religion in the world today that should be classified as a cult but no one dares because of it's size and because of "political correctness". I can't give you an exhaustive list of all that are cults. We'd be here for a bit. Martin was pretty thorough and noted the same. Many can be classified in similar categories by errors they share.
Some don't even know the language from which scripture comes. Martin complained for years about the Jehovah's witnesses who claimed all sort of things about the original Greek texts; but, of 5 people he was finally able to pin down as part of their translation team after 15-20 years of trying to get their names - 2 of them could not read Hebrew or Greek. If your translators can't even read the language they presume to translate, it doesn't bode well for their product. LOL
Most cults deny that Jesus was God incarnate. But this is not a global truism. Mormonism's big giveaway is that it's polytheistic. But it says that God is a man and that men can become "Gods" themselves. It doesn't deny that Christ was God, persay, they just pervert it in such a way as to make Christ just another god among many. It's a pretty big error that is not reconcilable with Christianity. But other groups Claim Christ to be God incarnate and then pervert everything he said such that the surface appearance looks right; but, everything they say after that is befouled.
As to what makes Pentacostalism "not" a cult is pretty plain. Pentacostalism largely believes the entire New testament is relevant - where many other groups say that certain things were only for first century, etc.. There are groups that claim to be pentacostal that do really whacked out things like dancing with snakes. This would fall under the category of "tempting God" at the very least and no real pentacostal would claim them as part of their group without calling them errant. You don't tempt God. Jesus said as much; but, evidently some claiming to be his followers don't get that or never bothered reading that part of scripture.
There are a good many things in scripture which Christians understand to be true. By and large your cult groups will say they actually mean something quite different and want to argue that things can be taken multiple ways (with the underlying implication that theirs is just as right as the next person's idea). There are not multiple correct ways to take things. There are multiple ways and one correct way. This, indeed, is why Christ spoke to everyone but the Apostles in Parables. Only the Apostles were allowed to understand what Christ was saying until Christ completed his mission here. He told the apostles that it was given for them to know, but not for the masses - not yet.
Is there some reason you ask my opinion?
There is only one reason they are considered cults and Pentecostals are not. Cults do not believe that JESUS is God's way to heaven. They do not proclaim him as the son of God and the way to salvation. Jehovah's witnesses and Mormons say he is teacher or prophet, but do not necessarily see him as way to salvation. That denies his deity as God and the scripture Jesus said "I am way and truth and life and no man enters to father but by me."
Pentecostals on other hand absolutely declare Jesus is Lord and only son of God and only way to heaven. We also believe in Baptism of Holy Spirit (second christian experience for those who want it) which includes the nine gifts of the Holy Spirit explained in I Cor Chapters 12, 13 and 14. Hope that is simple enough explanation.
> Which do you consider cults?
Cults deny the fundamental doctrines of the faith. Both Jehovah's Witnesses and Mormons deny the full deity of Jesus Christ and His equality with God the Father - but especially the Mormons are getting trickier all the time about this.