There is no right or wrong answer to this. Partly this is a taste and style decision. Some photographers prefer the mood created by darker backgrounds and some actors will favour that too.
One thing that should be considered if you’re thinking of going with a photographer that solely favours darker backgrounds is that peoples faces and hair don’t just merge into the background. Casting Directors want to get a quick impression of how you look, hair length and volume included. If it’s all merged into the background it won’t help. Photographers usually get around this by using some back light that will give some the hair some definition and provide that separation from the background.
So, apart from personal preference there are a couple of practical considerations that are worth thinking about. Firstly, if you’ve got blond hair then it can ‘pop’ nicely from a dark background. Equally if you’ve got darker colouring then that can contrast nicely with a lighter backdrop. Secondly, if you’re a guy with a shaved head then that can also ‘pop’ nicely from a darker background.
All of that said, with the right lighting either set up can look great which ever way around.