Main criticism of the bitcoin symbol denoting what we commonly refer to as sats, would be this.

The thing the most precoiners know about bitcoin is 21M units, if nothing else. Suddenly why is there more? You can explain that nothing changed just a naming convention, or you can explain there are 100M sats in a bitcoin like there are 100 pennies in a dollar.

And I mean I always liked the @ + s symbol.

The penny dollar analogy really makes it really easy to grasp.

Replace dollar and pennies with any other currency and its sub units.