I tested this, shorting SQQQ came a bit better than going long TQQQ. Problem is (i) you have to pay the short interest rate, which eats into, or eliminates, any advantage, (ii) you have to worry about short squeezes (although may not be too much of a concern if tons of shares out there), (iii) you have to find the shares to short in the first place, (iv) since its a short, you can theoretically lose an unlimited amount of money, (v) since its a short, the way these things work, every day it goes up, you have more shorted the next day, which means if it goes up again you have more shorted, so in a big, slow bear market every day the stock market goes down and your short goes up you are shorting more and more each day, further compounding your losses, (v) with the short, you always have to worry about the guy you borrowed your shares from deciding to sell his SQQQ shares, meaning you have to buy your shares at his whim - and the most likely place when he will want to sell his SQQQ shares is a market low (thus a SQQQ high), because he had made a killing, meaning you could be forced out of your position after you've suffered huge losses, right when you need to stay in the position to take account of the leverage to try and gain back some of your huge amount of losses as SQQQ has risen a ton on the market way down, and (vi) because you can be forced to buy to cover your SQQQ shorts, you will be forced to recognize any tax gain, and I want to make sure and hold until I die, so no taxes whatsoever.
I think TQQQ is the way to go for all these reasons. You'll still turn small amounts into HUGE amounts over the long run, without all these issues.
