A very good question... Both of it is profitable but if you will going to ask me i prepare participating in signature bounty campaign than mining....  In mining you needs a lots of time and money as you capital...  Unlike in bounty campaign you will not really lose here especially if the project you've join is successful....  But it will depend also on your the higher your rank the better...   But if you can engage both on mining and bounty campaign why not....  This two is really great....  Just work for it and learn as well....