Bhagavad Gita · Jnana Vijnana YogaChapter 7, Shloka 17 (7.17)

Shankaracharya — the self is dear. Jñānī tattvavit tattvavittvāt nitya-yuktaḥ bhavati eka-bhaktiś ca anyasya bhajanīyasya adarśanāt — by knowing the truth he is ever united, and since he sees nothing else worth worshipping, his devotion is to one alone; priyo hi yasmāt aham ātmā jñāninaḥ … prasiddhaṃ hi loke ātmā priyo bhavati — I am the self of the wise one, and the self is dear to everyone; sa ca jñānī mama vāsudevasya ātmaiva iti mama atyarthaṃ priyaḥ.

Acharya Ramanuja — love has no limit. Tasya hi mad-eka-prāpyasya mayā yogo nityaḥ, itarayos tu yāvat svābhilaṣita-prāpti mayā yogaḥ — the wise one's only goal is me, so his union is constant; the others' lasts only until they get what they want. Atyartha-śabdo abhidheya-vacanaḥ, jñāninaḥ ahaṃ yathā priyaḥ tathā mayā sarvajñena sarvaśaktinā api abhidhātuṃ na śakyate … priyatvasya iyattā-rahitatvāt — the meaning of "atyartham": how dear I am to the wise one, even I, all-knowing and all-powerful, cannot put into words, because that love has no limit. Example: Prahlada — sa tv āsakta-matiḥ kṛṣṇe daśyamāno mahoragaiḥ, na viveda ātmano gātram (Vishnu Purana 1.17.39) — even while being bitten by great serpents, Prahlada, his mind absorbed in Krishna, was not aware of his own body.

The difference: Shankara — the reason for this dearness is oneness of self; Ramanuja — the dearness is boundless love, with two in the relationship.