Depends on what is suitable for you. If you want to earn a good and decent amount then invest in trading and start doing it but first you have to learn about the market. Rewards of mostly Signature campaigns are not too high and you will need to work hard to earn through out the week, however few campaigns are rewarding handsome amount to the participants. Mostly of the users(including me) are doing both because these are not interrelated to each other and there isn't any effect of one work over other.
I am also doing both, joining signature campaigns and trading. Joining signature campaigns enables me to earn bitcoin and altcoin, it is true that some campaigns gives huge rewards due to succeeding but of course not all campaigns are like this. I have experienced joining campaigns that did not succeed and some did not give any rewards at all. The tokens that I am earning from altcoin signature campaigns are what I used for trading and some coins just really give good earnings.