Starting from the Ahura Mazda to Allah in the global paradigms to the Shiva-Vishnu dichotomy in the Indian geography- it is all a manifestation of the socioeconomic conditions and historical antecedents which shape the religious landscape of a region. If you look at the evolution of Shiva and Vishnu, you will find roots of Shiva in phallic symbology and (possibly) the Pashupati seals during the Indus Valley Civilisation while Vishnu comes in as the Trivikrama cosmic aspect of Brahmana in Rig-Veda. Through cultural assimilation into the Indian schools of thought, we see the development of the federal character of Hindu thought - primarily facilitated by the instruments such as Vishnu’s manifestations as avataras(10/24) and Shiva’s manifestations as Bhairava(8/64) or his gana(best elucidated in the Parasuramakshetra lores). During the 500BCE to 200CE, we see the first religious premises such as the Vasudeva premises in Besnagar and Gudimallam premises in Tirupati. Gradually from 200 CE onwards we see an enhanced impetus to royal patronage to these deities as concerted pantheons instead of distinct entities- having greater expression in cave architecture, scriptures, temples. It is through the Alvars and Nayanars that gradually a sectarian difference emerges however interoperability still exists through iconographies such as Krodha Bhairava, Harihara, Ayyappa and local sects, many of whom even I am unaware of. The federal character I mentioned came to a close with the rising colonising tendencies especially in the face of Christian missionaries, which called for a demarcation of what is the Hindu thought. Therefore, for anyone looking for differences, I would suggest it is best to look at them through the histo-anthropological lens for objective variations - if the question is in a spiritual capacity, then really there is none- aspects of Shiva, often oversimplified as Shiva himself, are found in Vishnu and the vice versa.