As most will know, there are 2 Borgia series running parallel with each other. The Borgias starring Jeremy Irons is the one most watch or know; it being stylistically similar to the 'The Tudors'.
'Borgia' by comparison, is slower paced and grittier. What flashes by in half an episode on 'The Borgias', is detailed over an episiode on 'Borgia'. I make no pretence at being a historical expert on either Italy or The Borgias, but of the 2, 'Borgia' appears more authentic. This might have to do with the quality of writers on board, including Larry Cohen (In Treatment) and Gina Gionfriddo (Law & Order). About the accents: I readily confess, it took me an episode to attune myself to John Doman who sounds like he just stepped out of The Godfather (actually he stepped out of The Wire), which I suspect was the producers intention, as there are obvious comparisons between The Borgias and The Corleones.
To sum up I am enjoying both series, but if I had to make a choice as to which one I would invest my time in, it would be 'Borgia'. That said my instinct tells me 'Borgia' might be cancelled before the story is finished.