All hindu gods (countless gods !!) often confuse average minds, when god is ONE, hinduism has numerous gods. Gods are representative of nadis in the human body. Nadi is a sensitive neuro zone, but it is more of spiritual center. If all these nadis are intact, then it gives raise to kundalini and other spiritual chakras.
A farmer is interested in rains, so he prays Lord Indra. A terrorized person may invoke Lord Narasimha to get instant help !!(so long he is calm & concentrating on lord). A student may pray to Goddess Saraswati for knowledge and doing good in exams, while a qualified graduate going for job interview may pray to Lord Ganesha.
So each hindu god is represents a nadi (spiritual force center), when the mantra is recited with concentration, that nadi gets activated
Gayatri mantra is supreme and activates all nadis at a time, so it is most powerful mantra. By reciting this single mantra, it is assumed or equivalent to all other mantras.
So in short there is no difference between terminology of bhavan and bhagavant. These are human terms, cannot transcend the gods or demi gods.