I tested a bunch of these ... I really wanted the simple look of this one:
(a) $5-$15ea -
https://www.aircraftspruce.com/catalog/elpages/eadualusbpanel.php
But the one that ultimately worked best and provided true 5A (2.4 per jack) consistently was this one:
(b) Blue Sea Systems - $45ea -
https://www.steinair.com/product/dual-usb-panel-jack/
I tested by draining an iPad and iPad mini to dead and then plugged them both into the charger. "B" charged them both simultaneously as fast as the large Apple wall charger. "A" took hours and one of the iPads constantly dinged because it was loosing a connection. I did this 3 times for each charger, just started a test nightly before I went to bed.
I didn't stop there and really wanted the simple clean look of the "A" type chargers so I ordered a half dozen different brands, different sites. Some actually were different, however, most were just the same (Chinese?) unit repackaged and rebranded. All of them did the same thing in tests, the ones that worked anyway.
With a two place airplane and both people having smart phones and iPads, I extended the test by connecting two chargers to one 12V regulated source, 4 USB ports total.
The "A" units performed the same, horribly. After a few hours of constant disconnect "dinging" I just stopped the test.
The "B" units took whatever I threw at them like a champ, at one point having 2 dead iPhones, and 2 dead iPads sucking on them like a newborn, didn't skip a beat! The 100% charge times were within a few minutes of the solo test and they never even kicked the fan on from the power supply, highest draw was just over 10 amps as expected, average was around 4 amps.
The final test was all 4 devices playing video for an hour, surprised to say the chargers kept them at 95-100% power the entire time. I just stopped at an hour concluding that I was at that point just being excessive in my testing.
The "B" units (I purchased from SteinAir) just didn't have any issues at all. The bevel is larger and there is undesirable branding that I don't like, I doubt anyone but me would notice.
While very slow charging, most the other units did fine with just one device connected, but just one port at a time, the secondary port would simply drop to half an amp or lower.
Not scientific or exhaustive, but close enough, hope it helps!