I would not bother with a small unit. You can still find the Hornady Hot Tub with a quick search. Get that instead if you want to go Hornady. It is what I currently have after having others of various sizes. Another option is the Lyman Professional. I have not used it or really looked into it, but it is big enough. Stay away from the generic 'commercial' stuff on Amazon (been down that road).
The problem with smaller units is they do not have enough transducers - they won't make enough ripples unless you only put a very small amount of stuff in them.
The Hot Tub only comes with 1 basket and 1 pan. I picked up 2 more pans. I got them on Amazon, but I recall I had to look for a while before finding them. The Hot Tub is not designed to take more than 1 (you use either the pan or the basket) because of the tabs for the parts hangers but I just notched out pans to make mine hold 3. By doing that I can put clean tap water in the unit and solution (cleaner and distilled water) in the pans. I can clean about 400 pieces of rifle brass with less than a gallon of mixed cleaning solution.
For cleaning solution, I have tried the home recipes. Nothing works like the Hornady Brass (not Gun) cleaner. Regardless of the solution used, you need to rise well (probably already know this from your pin tumbler). I put my brass in large pistol ammo trays (open bottom trays) after rinsing them and blow the water off with a compressor then stuff them in a brass dryer (I have the FA). Rather painless process.
No matter what you do, it won't work as well as a pin tumbler. If you are expecting the super shine, everything perfectly clean, you will be disappointed. Still, you are not cleaning up pins and it has other uses beyond brass. I pin tumble my semi-auto brass to make sure everything is gone, but I only do it outside in the summer months. From a manual labor perspective, an ultrasonic takes less effort. However, the cleaning itself does take more time. I dunk a few of my pistols and the AR's, but only when completely stripped.
If it were not for the amount of time I spend making sure my case mouths are as perfect as I can get them I would probably just stick to a media tumbler for my bolt gun brass. But as it stands today, I am using an ultrasonic.