No experience with GRAPH, but I do have a lot of experience with SCL.
LAD, FBD and SCL puts in some branching and formatting code that may not be necessary for the intended function. The LAD, FBD, GRAPH and SCL generate STL code, but you probably mean to compare against STL code that is manually optimised by the programmer.
My estimate is that LAD and FBD adds 25% more code than optimised STL.
And I estimate that SCL adds 50-100% more code than optimised STL, but a lot of the added code consists of jumps, so it will not mean that the execution of the code is 50-100% longer.
But I also think that it is not very relevant to optimise code as it used to be in the past. Todays CPUs are 10-20 times faster than they were 10 years ago. And this development will continue. It is more important that the code is easy to maintain, than that it is optimised for speed.
(Peter Nachtwey who make code for motion controllers will disagree.)