fishing is easier to level up and will get you more money in the short run. However, mining is one of the most profitable skills at high levels (85-90+), but will not make you lots of money until you are pretty high up (also it takes more time, patience and dedication to do mining).
So if you dont plan to invest much time and just want a good way to make quick money do fishing, but if you want to make serious money and dont mind spending LOTS of time then do mining.
So if you dont plan to invest much time and just want a good way to make quick money do fishing, but if you want to make serious money and dont mind spending LOTS of time then do mining.