Compositing shader: different modes in one shader?

Hi,
I'm looking at the composite.shaders-help file (in Examples -> Jitter -> Render -> Slab).
In this example, when you select a different blend mode, you load a different shader file.
Would there be pros/cons in using a single shader with a if/then/else if/then/else if/then... (or case...) to address the different compositing modes?
Where should I look for an example of shader with if/then/else testing a value given in a right inlet for jit.gl.slab?
Thanks for any pointer in the right direction!
J-F Charles.