They are obviously not the same show, Succession is loosely based on the Redstones and Murdochs and Billions is loosely based on Steve Cohen, Preet Bharara and Eliot Spitzer.
They are both however, depictions of extremely rich elite members of New York society who wield power greater than many can dream of. Billions depicts them as larger than life figures, full of wisdom, guile and general suaveness, while Succession doesn't pay such deference to them, Kendall is a fukking druggie/klepto, Roman is a sex pest who can't actually have sex (mostly thanks to excessive drug use), Connor is Connor and Tom is a loser. Logan is probably the least pathetic but would Billions have Axe piss on the floor in a state of confusion?