The performance of the Harbor Freight units are less than inspiring.
Might be OK if you could run them continuously, but you can't - only 480 seconds maximum on the timer.
The results on dirty cases are very similar to using the same cleaning solution in my vibratory tumblers.
If you look at the picture of the Hornady, and go shopping on Ebay - you'll find the same "unbranded" unit for considerably less than the stated retail. I haven't had any direct experience with them.
I'd buy some ceramic media for the short term, and save your money for a used or new commercial ultrasonic cleaner unit and be done with it.