To begin with, these poets are all writing in the Victorian era. A definite similarity between the three is that all might be considered monologues, in that they are spoken by a speaker to another persona within the poem (though Browning is the most famous for using the monologue form).
Arnold and Tennyson are extremely concerned with the thematic issue of faith, which plays a prominent role in both "Dover Beach" and the opening of "In Memoriam." In these poems, faith figures as a way to connect with others (the speakers connect with the addressee of the poem in "In Memoriam," and with others across time and space, such as Sophocles, in "Dover Beach"). By contrast, Browning's poem specifically rails against ideas of faith and human connection, in that the Duke has had the Duchess killed and he sees no harm in it, even boasting about it to the poem's addressee.
Another difference between these poets is in their use of form. Browning and Tennyson are writing in defined poetic forms: Browning uses the classic form of the heroic couplet (two lines of iambic pentamenter that rhyme together), and Tennyson uses the "In Memoriam" stanza, a stanza structure that he has created specifically for this poem and that consists of four lines of iambic tetrameter rhyming ABBA. Both do not break their rhyme and meter. Arnold, on the other hand, while he is certainly conscious of the effects of the variable rhymes and rhythms present in his poem, adheres less strictly to form. He includes stanzas and lines of varying length and stress; he is essentially writing in an early form of free verse. The freedom of Arnold's form mimics the poem's boundless message of, "Ah, love, let us be true / to one another!" The restraint depicted in the other two poems, however, perhaps suggests Tennyson's speaker's attempt to reign in and control his grief through the structure of poetry, and, on a darker note, hints at the dark self-control of Browning's murderous speaker.