What is the difference of 犯不着 用不着 and 犯不上？
[犯不着/犯不上]为这点小事生气。 oral chinese
用不着为这点小事生气。mostly we use this way in written.
they are all ok. and the meanings of 犯不着/犯不上/用不着 are almost the same. it's up to you.