i dont think you should compare both , bcoz in cloud mining you need knowledge as well as capital for investment . also you have to trust the company who provide this service , and he will deduct his own cost+profit , so less returns in compare to own mining .

while signature campaigns only need your best knowledge , helpful nature towards community , activeness in forum and quality posts . no need of money to invest , just need 30-40 minutes daily or 3-4 hours in a week . and you only need to post 10-20 quality posts in a week and you can earn merits and reach to high rank to get more stakes .

so i will recommend you signature bounty if you lack fund . cloud mining if you lack time .