so deltatime mainly benefits in case of a slower computer?
No, if a computer is fast the game will run fast (and vice versa), but if your program uses vertical sync the fps cant exceed the refresh rate.
The point is that you want your game to look like it runs at the same speed whatever the speed of the computer.
But go with what LarsG said above, IMO its better to use vertical sync and keep your code tight. I keep my programming computer (this one) reasonably low spec, so if it struggles with my code I know I need to do some optimizing.