What is more payfull in animation 3d modelling --rigging- animation or compositing?

depends on how good you are.

modelers are a dime a dozen and are usually outsourced to Asia, unless your freaking amazing.

rigging is very technical and is harder to find somebody really good at it. A friend of mine just got hired on at pixar for an apprentice ship, they are starting him off at 60,000 which is pretty amazing for entry level.

Animation pays pretty well too, but competition is fierce and would require you to go somewhere like cal arts which will set you back about 70k per year i believe.

Compositors I've known a few people who've tried to become compositors. Didn't work out to well for them, they went into lighting, which is similar in a lot of ways. Compositing jobs are few and far between and are usually filled by highly experienced compositors.

I could be wrong, these are just my observations, im a texture artist/shader writer myself. The main key is be absolutely sure you want to do this if your looking into it, see what you like to do the most, Become the freaking best at whatever you decide to do and then maybe you'll get to see how much that pays. Hope that's helpful