A lot of shooters like to say that a "heavier" bow "rips" the string from their fingers. "Rip" in this instance, being a good thing; whether that means "smooth" to you, you'll have to determine for yourself.
I find it easier to get "off-the-string" with a heavier bow but do not have a problem with my release shooting light either. Release is something we all have to work on, whether we shoot heavy or light.
String angle likely plays a greater roll in regards to a smooth release, as Red Tailed Hawk mentions above.
Good shooting -
Kris