The primary distinction between the intellectual poet and the reflective poet in "The Metaphysical Poets" by T. S. Eliot is the capacity to think versus the capacity to feel. He gives the example of poets like Tennyson and Browning, whom he considers to be intellectual poets and who "think; but they do not feel their thought as immediately as the odour of a rose." He goes on to contrast this with a poet like Dante, for whom "a thought ... was an experience; it modified his sensibilities." Eliot is not necessarily saying that the intellectual poet cannot write great poetry but rather that the feats of their poetry often hide the absence of something deeper, the absence of a greater level of emotional reflection on the thoughts that are being expressed.
Eliot goes on to say that, while the movements associated with the intellectual poet improved and refined the language we use, "the feeling became more crude." He points to poets who revolted against this era of thought: those who reflected more deeply on their experiences through emotions. Eliot specifically points to Keats and Shelley but notes that they both died young, while other poets of their era, such as Browning, continued to write in the manner he associates with the intellectual poet throughout their long lives.
Part of the critique Eliot sets out here is geared toward larger social criticism. He claims that society seems to think that
the more intelligent [the poet] the better; the more intelligent he is the more likely that he will have interests: our only condition is that he turn them into poetry, and not merely meditate on them poetically.
While Eliot realizes that the reflective poets he refers to have faults, he also believes them to have a better balance toward understanding feelings and the mind. This strikes him as being both more mature and more likely to "age" better as time passes; after all, the intellectual poet is greatly tied to the civilization or society they write in rather than the broader, more universal human condition of the reflective poet.