I tend to roleplay a little with each character. Michael is mostly law abiding, only committing serious crimes out of necessity (sod driving laws, though!). Franklin is pretty similar, but Trevor is... unique.

If someone beeps at Trevor, he drags them out of their car and beats them to near-death. If someone dents his car, he drives them off the road. If someone exists anywhere in the vicinity, he's like to insult them. It's great fun.