Well in my opinion signature campaign are best and more trusted , because in signature campaign you only need to invest your time not money and you can earn coin by promoting projects apart from it you learn a lot about Crypto currency , new projects upcoming with new technology.

In cloud mining you have to invest money , and you are not sure that you will get your investment and profit amount back , because mostly are ponzi scheme. If some are not it can't be reliable as they may shutdown their services without informing.