How would you describe the contrasts in Othello and Iago's perceptions of love?

Iago and Othello seem to possess contrasting ideas of love. One can interpret each man's thoughts on love from his associations with others, and, more pertinently, from his relationship with his wife.

In Act I, it is clear Iago sees (what he believes to be) love as a tool to be used when manipulating others. He has a cynical understanding of the term. When Iago first uses the word 'love,' he expresses its negative connotation. He tells Roderigo in Act I, scene 1:

...But he; as loving his own pride and purposes,... 

In this instance, Iago criticizes Othello's love for himself and his ambitions, suggesting the general is displaying a boastful pride in his own status and future aspirations. Such a love is selfish and self-serving. Iago also states that he would show love to the general insofar as it serves his own purpose. The love Iago speaks of is not real, but part of an act. He says,

...not I for love and duty,
But seeming so, for my peculiar end:...

Iago later appeals to Brabantio's love for his daughter as a means to urge him to take action against Othello, who, Iago and Roderigo claim, has abducted her. 

'Zounds, sir, you're robb'd; for shame, put on
your gown;
Your heart is burst, you have lost half your soul;
Even now, now, very now, an old black ram
Is topping your white ewe.

After the two demonize Othello in Brabantio's eyes, Iago leaves to be with the general for, as he puts it:

I must show out a flag and sign of love,
Which is indeed but sign.

Iago has to create the impression that he supports Othello out of love and will stand by him against Brabantio's accusations. It is all just a show, as Iago actually despises Othello. In Scene 3 of Act 1, Iago reveals his true feelings about what he believes love to be when the lovesick Roderigo expresses his desire to drown himself since Desdemona will be leaving for Cyprus with Othello:

...but we have
reason to cool our raging motions, our carnal
stings, our unbitted lusts, whereof I take this that
you call love to be a sect or scion.

It is merely a lust of the blood and a permission of
the will.

Iago deems love to be merely a feeling of lust and desire. It is a curse and meaningless persuasion of the body, not the heart. Iago later expresses the same kind of sentiment when he talks about Desdemona's love for Othello and says that if she had been blessed she would never have loved him, implying that her so-called love is actually lust.

In his monologue later, Iago says he loves Desdemona, not out of lust but because his supposed 'love' serves a different purpose:

...Now, I do love her too;
Not out of absolute lust, though peradventure
I stand accountant for as great a sin,
But partly led to diet my revenge,...

There are a number of instances in which Iago expresses his love for Othello, but this is merely part of his plot to manipulate the general and win his trust. Iago is entirely convincing and Othello becomes completely ensnared by his web of lies. Further evidence of Iago's inability to love can be found in the fact that he never expresses any soft sentiment towards Emilia, his wife. He does, however, abuse her love for him to get what he wants, such as Desdemona's precious napkin.

In contrast, Othello seems to be a genuine disciple of love. He states as much when he explains what led to his and Desdemona's elopement in Act 1, Scene 3:

...I will a round unvarnish'd tale deliver
Of my whole course of love; what drugs, what charms,
What conjuration and what mighty magic,
For such proceeding I am charged withal,
I won his daughter.

...She loved me for the dangers I had pass'd,
And I loved her that she did pity them.

We know that Othello has real feelings for Desdemona because he continuously expresses his love. Upon his arrival in Cyprus, Othello says the following when he sees his wife:

It gives me wonder great as my content
To see you here before me. O my soul's joy!

He constantly uses terms of endearment such as "sweeting," "love," "dear love," and "chuck." It is clear Othello dotes on Desdemona and is a devoted husband.    

It is the cynical and malicious Iago who taints the purity of Othello's love. His insidious lies and manipulation drive the general insane with jealousy, so much so that he falls into a fit, rejects Desdemona's advances and, at one point, slaps her in public. When he decides to suffocate Desdemona, his anguish is quite clear, for he still loves her. He approaches her while she is still sleeping and repeatedly kisses her, saying in Act 5, Scene 2:

Ah balmy breath, that dost almost persuade
Justice to break her sword! One more, one more.
Be thus when thou art dead, and I will kill thee,
And love thee after. One more, and this the last:
So sweet was ne'er so fatal. I must weep,
But they are cruel tears: this sorrow's heavenly;
It strikes where it doth love.

When Othello later realizes his actions were borne from Iago's malice, he cannot forgive himself and, filled with remorse and regret, commits suicide.

It is clear Othello and the amoral Iago have entirely different perspectives on what it is to love. Iago clearly sees it as a weakness which can be exploited whilst Othello, who has been genuinely touched by love, forfeits it by foolishly succumbing to a greater weakness—insecurity. Both these sentiments are ruthlessly exploited by the malevolent Iago.