I have not much experience in PCB ultrasonic cleaning (I try to use them the less possible to avoid damaging some components), but it's since 1995 that I use them to clean small mechanic parts. In that particular sector, I can consider myself as an "experienced user".
In my opinion differences are in:
1. power/litre ratio
2. no. of transducers
3. tranducers positions
Branson is a respectable brand in ultrasonic industry, also for reliability: we had branson cleaner at work turned on for 8h 3-4 days a week for many years with heating on and had no issues at all. The tank was still perfect with no corrosion.
Since I worked with Brandon cleaners for 12 years I can't believe they don't work properly; if it was really like Louis was reporting in the video, the Branson had a fault.
In my opinion, it would had be better to compare them with the alluminium foil test to make a proper comparative test and see if the Branson had a fault.
The sweep is helpful to avoid stressing some components and to avoid dark spots. But since different brands use different sweep timings (for example Branson uses a quick 4Hz sweep while Elma 1Hz) you can have different results (quicker or slower cleaning time) but a board/component should came out properly cleaned in any good ultrasonic cleaner with a proper cleaning time and proper solution.
37KHz are a general cleaning frequency and is a general purpouse that can be used on any "general" part.
They (manufacturers) say that +125KHz are much gentle and can clean most sensitive parts without damaging them, but I don't bet on it with quartzs and mems.
Generally speaking the higher the frequency the smaller the spot the cavitation can reach (so it cleans smaller spaces) but less "violent" is the cavitation, so the cleaning action.
Comparing ultrasonic to a toothbrush, 25KHz are hard bristles, 37KHz are normal bristles and +125Khz are soft bristles.