I prefer long-term investments. I tried short-term investments, but I did not succeed, so I focused on long-term investments. 
Yes in long term investment in both bitcoin and ethereum you will definitely without doubt get a good profit in both currencies and tension in long term investment is also less
In short term investment there is no big profit will come and the rate changing tension will come in our mind.
So i prefer long term investment is the best investment for all investors.