Both trading and investing are risky however if you are not profitable in trading why not try long term and just leave the coins you traded with, not unless if you really really need the money and you have to withdraw them weekly or monthly. Investing is also the same thing but much riskier especially if you have invested in some fake coins then chances are zero or something.
Trading, at least short-term, is vastly more difficult than investing (for humans). Short-term movements are essentially unpredictable for the vast majority of people. Investing on the other hand, takes quite some effort with regard to due diligence, but that's something that simply requires some time spent researching. The most difficult aspect of investing is balancing a portfolio, which needs a way to at least qualitatively asses risk.
Either way, I would add
AiCoin to the list. Poised to be a very stable and successful coin that avoids almost all of the risks of short-term trading, while reaping its profits regardless, while at the same time being in a position for massive gains due to investments in ICOs and other Machine Learning or Blockchain related start-ups.