Oldsarge,

You're right about the popularity of these guns in Europe. Here in Brazil the same happens, and because of the less complicated rules involving smoothbores, they are far more popular than rifles (keep in mind that in some places, even a rifled choke is also considered a rifle).
Anyway, although they are not Paradoxes by any definition, these smoothbore slug guns are actually very effective. Accuracy at 100metres is a plus, but not really necessary on the type of cover that we find here. Mostly, game is shot at 25-30 metres. Another thing that substanciate the choice of a smoothbore is that Brennekes and Fosters are available everywhere, and the Paradoxes and Faunettas required an especific type of projectile.