The form, name and attributes of God differ from culture to culture, Muslims call him Allah, Christians Abrahamic etc, unfortunately many pseudo guru(S) are also seen stating the indifference between the God worshipped by Abrahamics and Hindus. Factually it is not the case, as the God propagated by Abrahamics is very weak, cruel and less intelligent, while the God who is worshipped by us is all-knowledgeable, all-blissful, all-powerful, in other words He is completest.
Still due to different traditions (Sampradaya{S}) of Hinduism, people get confused and fight over the supremacy of different form of Bhagvan.
But what is the truth? Who is supreme? Vishnu or Shiva? Or is it Durga? Or someone else?
Well we have to understand that the same supreme personality appears differently in 5 forms to perform 5 different activities. For creation of the universe he assumes the form of Hiranyagarbha Brahma, for its sustenance he becomes Vishnu, to annihilate it he becomes Shiva, to punish the wrong-doers he assumes the form of Shakti, and to bestow his mercy, he becomes Ganapati.
These 5 forms are complete and non-different from each other and a person can accept any of the forms or the forms of these primary forms as his Ishta-devata. (For example Rama, Krishna, Varaha come under Vishnu-tattva, Bhairav, Hanuman come under Shiva-tattva, Surya, Brahma come under the Hiranyagarbha-tattva, Durga, Kali come under the Shakti-tattva)
These 5 forms are also known as Pancha-devata(S) generally and only the forms of these forms can be worshipped as Ishta and Kula dev/devi.
To conclude Bhagvan is one, but as he is all powerful he assumes 5 different forms which are also his complete manifestations, thus there is no difference between any form of that Bhagvan.
Just like a single person can be a father, husband, son and a brother, similarly, in accord to the desire of devotee, Bhagvan assumes different forms.