Not really…
Southerners recite Gam which seems more accurate and ancient based on Paninian Sanskrit.
One is गं (gam) and the other is गङ् (gan) - a work named Varnabijakosha specifically says to utter the mmmmm sound - so I would go with Gam. The Bindu here is not (ardhabindu) or nasal but Purnabindu (anusvara), which is crucial for Bija-mantras (seed sounds). The mmmmmm sound should radiate from the third-eye chakra all the way to a place is Shodashanta, which is astrally located a little above the Crown chakra.
The elaboration of the seed sound of Ganesha is split into G - a - M - where Ganeshopanishad explains it as Brahma - Vishnu and Shiva - with Shiva represented by “panchama” - which here means the fifth letter of the “pa” category which is “m” - with ardhabindu or half sound gan - the “m” or the shiva aspect does not come forth.
The mistake a lot of folks make is applying rules of vocal language to Bijas (where one would apply the rules of following Om with Gam, which would even make Om as Oan) - which is not accurate as these need to be understood from the perspective of the Tantras where combinational sandhis (compounds) do not apply to Bija sounds as these are not meaningful words that are guarded by normal grammar.
That said, this is one of the cases which are still acceptable either way (probably) considering the other horrendous forms out there on YT.