I think the best investment will be the USDT. The rate of the Ethereum and Bitcoin falls very quickly and there are no signals for future growth.
Good joke buddy, meaning of investment is to increase the profit with your money. If you invest on USDT it will be in the same price after 10 years as well since the market value of USDT centralized coin is defined in that way mate.
So all the time investment relay on the both the coins BTC and ETH really worth to invest your fund. Please put your investment on right way you think and get the review about the thing you want to invest for your good deeds.