NACS is dramatically easier to maneuver into the port on the car, and supports higher amperage. CSS requires an extra internal flap on the car side that you have to open and close manually, as well. It’s a seriously underwhelming design.
By combining DC and AC onto the same pins, it reduces the part count and weight of bus bars / conductors which run from a car's charging socket and the battery.
NACS is a better user experience for people and significantly so for people with mobility issues, disabilities, etc.
The pre-eminent NACS fast charging network is markedly better than the totality of all CCS1 charging networks.
I've used both and while from a technical standpoint CCS might be superior (I have no idea), in practice NACS is sleeker and feels less clunky.
Is that a good reason to adopt a standard that isn't open? Probably not. Does the average customer cares and will it have an impact on their day to day? Probably not.
EDIT: Seems like NACS is open after all so I don't really understand why we would bother with CCS.
It's open in every respect that matters, but pedants will rightly point out that it hasn't been submitted to a classic standards body (like SAE) to formalise in the way that satisfies middle management and expensive consultants.
The form factor is significantly smaller, which means it’s easier to use. But more importantly the charging connector has no moving parts. A common failure on CCS chargers is that the locking pin breaks and the charger will no longer stay firmly attached to the vehicle causing charging issues. On the NACS adapter the locking pin is on the vehicle.
Charging infrastructure sees significantly more duty cycles than an individual car so it makes sense to move the wear part to the vehicle.
Even with CCS1 the US was out of sync with "the rest of the world", which uses a few different connectors.
And in the end it doesn't really matter. I'm not driving my car across the ocean very often. Import processes already tend to make taking a car from one continent to the other a huge hassle, so to the vast majority of people its probably easier to just sell the car in one place and buy another on the other shore.
