I checked yesterday with a Dell-Chat support and the told me there is no difference between the models. They are the very same monitor. It's a problem of the reseller (here Digitec) that used two difference model description mostly because they come from different reseller.
In the meantime, this one is also sold as A, even if the TechDetails still say non-A...interestingly, however, for 8 CHF less than the "special offer" of the real-A at 368CHF :D