Biggest con was collision and AI racing lines. No Ferraris or Lamborghinis was fine, there were alot more cars to choose from. They would have been nice, but no license, so that wasn't really fully under their control. Body kits, don't care for in GT. It's a racing game, not a car dressup game.
The AI racing lines though were on a string. That, and very unrealistic collisions with walls and AI.