I think it depends on the cat. Our lovely sisters didn't have a weight problem, but current cat does and tends to beg for food (Rescue cat, food issues!). She has lost weight on diet dry food and is now on Royal Canin satiety dry food and it does seem to help.
FatCatSlim was on the Royal Canin satiety diet and lost 1kg. He's now at his target weight and I've switched to an ordinary non diet food. What I am being careful about is weighing out the right daily amount and only letting him have that.
I think that provided you keep an eye on what they are eating and their weight is good then feed them whatever food they like.