Very good topic, no learned scholars to answer the question however. Firstly you need to clearly state what are the tenets of Sikhism and Vedanta, only then can you compare them.
Vedanta is one of the 6 main schools of sanatn dharam
Core mantra is ahm brahm asmee - the jeev atmai is a part God
The path to God is four fold 1. bhakti yog 2. gyaan yog 3. karam yog. raaj yog
The term Vedanta means in Sanskrit the “conclusion” (anta) of the Vedas, the earliest sacred literature of India; it applies to the Upanishads, which were elaborations of the Vedas, and to the school that arose out of the “study” (mimamsa)
of the Upanishads. Thus, Vedanta is also referred to as Vedanta-Mimamsa (“Reflection on Vedanta”), Uttara-Mimamsa (“Reflection on the Latter Part of the Vedas”), and Brahma-Mimamsa (“Reflection on Brahman”).The three fundamental Vedanta texts are: the Upanishads (the most favoured being the longer and older ones such as the Brihadaranyaka, the
Chandogya, the Taittiriya, and the Katha); the Brahma-sutras (also called Vedanta-sutras), which are very brief, even one-word interpretations of the doctrine of the Upanishads; and the famous poetic dialogue, the Bhagavadgita
(“Song of the Lord”), which, because of its immense popularity, was drawn upon for support of the doctrines found in the Upanishads.
No single interpretation of the texts emerged, and several schools of Vedanta developed, differentiated by their conceptions of the nature of the relationship and the degree of identity between the eternal core of the individual self (atman) and the absolute (brahman). These range from the nondualism (Advaita) of the 8th-century philosopher Shankara to the theism Vishishtadvaita; literally “Qualified Nondualism”) of the 11th–12th-century thinker Ramanuja and the dualism (Dvaita) of the 13th-century thinker Madhva.
The Vedanta schools do, however, hold in common a number of beliefs; transmigration of the self (samsara) and the desirability of release from the cycle of rebirths; the authority of the Veda on the means of release; that brahman is both the material (upadana) and the instrumental (nimitta) cause of the world; and that the self (atman) is the agent of its own acts (karma) and therefore the recipient of the fruits, or consequences, of action (phala). All the Vedanta schools unanimously reject both the heterodox (nastika) philosophies of Buddhism and Jainism and the conclusions of the other orthodox (astika) schools (Nyaya, Vaisheshika, Samkhya, Yoga, and, to some extent, the Purva-Mimamsa).
Vedanta and the other 5 schools of thought only describe a particular part of God. However Sikhism is all in all ie complete in every way and incorporates all the different schools of sanatan dharm. The other difference i know of is that Gurbani emphasises union with God through shabad surat marg which is missing from sanatan dharam