I've got over 200 various clips from the show during it's N&A incarnation, and the one thing that really sticks out is how little Rick offered the show in terms of comedy. I actually rate him higher than Artie as a stand-up, but as a radio host, it was better that he left--you could tell as time went on that he was fed up with Artie's long-winded stories, but more fed up with the fact that he himself had precious few to offer in return.
As for Artie's intellect, it begins and ends with whatever books he last read and movies he last watched. He's in a bit of a time warp comedically. He's smarter than he'll let on, but I'd never call him an intellectual. At the very least, he's smart enough to have left politics off the show. Nick would have done well to do the same; he might still have been employed.