A cup/lightened 172 with 200 bhp or more would already leave a Mk2 V6 in the dark on power to weight. A 225bhp with the weight of a cup would slaughter it. Anybody going to the Renaulsport track days will regularly see slightly modified cups lap faster than V6s.
Now, having said that, I love the look of the V6, the engine note must be great, they are more exclusive etc. If there was some way to shed 300Kg off the V6 or to increase its power to 300bhp, that would be a great car.
Personally, I will probably stick with the lightest clio I can get, and make it lighter+more powerful. Cant go wrong with that. If I didnt need occasional rear seats, I would go for a caterham/elise instead. Not a V6.
So,,, roll on 225bhp 2005 clio. Ill be the first UK customer!