WRC cars are much quicker. Remember Colin McRae did sweeper at the Donegal Int in his 6R4 Metro? The all the locals in WRC cars where setting considerably faster times.

You do see metros still being used but they aren't the original Austin Rover 3 liters they are modern 2.5l jaguar engines with 425+bhp and more torque(Mountune may build them iirc), they also have more modern steering, suspension and braking components so in the right hands they can be reasonably competitive.