In my experience, enemies tend to lose track of you and shoot you less using silencers. As long as you hit the harder shots silencers give you, the game becomes easier using them. It's a tradeoff, and I, for instance, hate the lower bullet velocity and I welcome every enemy shooting me at once.
So, I can tell you they definitely add a benefit, but i cannot give a precise opinion on how good they are cause I hate them.

yeah I'm getting a lot of complaints about silencers, I do think enemies not hearing bullets makes a difference but the difference isn't very obvious. In the demo silencers did extra headshot bonus but didn't have reduced muzzle velocity, brining headshot bonus back and keeping reduced velocity might be a more interesting dynamic.