Countrary to the general opinion above, I actually think the Pirelli P Zero Nero are best in the wet and was in fact hoping for better performance in the dry. I was able to try them on a very wet day around Spa and if you look at their design they are quite heavily grooved. The perfect tire compromise does not exist. you either get very grooved tires which will be great in the wet, or little grooved tires which will perform better in the dry. If you get soft compound they will be good everywhere but will wear fast. When you change tires, the most vivid impressions you have on their performance is when you last drove the car on them. Naturally if you are changing tires in 90% of the cases it will be because they are worn and once you changed them you set off on a new set, it's only natural then that the gap in performance seems substantial and in favour of the new set.