I would say that Black Plague is much much more scaryier. I loved both and beat both of them a few times acually. But in Overture just knowing I have a melee weapon which will kill any dogs basically makes it feel that much safer. In Black Plague also having clarance around and the atmosphere in general I thought was scaryier. But as someone said the fact you can run away so easy from the infected is the only downside. But it does have more moments where thing's jump out at you. I remember near the start after getting the gas mask my way back.
Heard a door break loudly and run without turning around.