I think that's a bit of a sweeping generalization. It depends on the power to weight ratio, the way the power is delivered, and to some extent the drivetrain/mechanical grip on offer.
My TT has 250BHP, never feels anything more than "enough" power-wise, but the car is pretty heavy and the N/A V6 likes to be revved, the power delivery is smooth.
The 306BHP S3 on the other hand spools up and can become a bit lairy depending on the conditions, the power delivery is not smooth at all, it also (weirdly) weighs less than the MK1 TT.
250BHP in something as heavy as an A8L or long-wheelbase 7-series would never be too much to exploit on the road.