I think the main differences are diameter and weight. My Nardi competition is 330mm so it's a little more aggressive than stock, also because it's so lightweight i don't think it would be the best for daily driving on rougher roads.
I think wheel offset is a subjective thing, and you can also play around with it depending on the your boss kit and wheel depth. With a HKB boss and little offset on mine, I find it's hard to get a comfortable legs vs arm placement (more due the AW11 design than anything else I think), but the wheel itself feels like its in the right spot when using stuff on the wheel stalk, like AUTO-DRIVE :)
I really like the leather padded Nardi Gara series.