I think there are two variables in this, the first being the turbo.
I've never heard a PD100 make this noise, but cars runnign similar setups on the same turbo often produce different results too.
The second, and which i think is more likely the case, is the exhaust. I think its down to the shape of the exhaust, and the bends.
The leons always seem to make the noise louder than the
ibiza's. They have a longer straight section at the end of the exhaust. I think this is the reason why.