Well, seems that pipes really transfer they full capacity, as described on the tooltip.
I made a test with two Huge Bronze Pipes (9600mb/sec, with shutters) attached to a Quantum tank, and a fluid regulator set a 480mb/T (9600mb/sec) attached to another Quantum Tank.
Both tanks had shutters and machine controllers, set to be open by the same lever.
On the first test, I activated the lever, and after a few seconds, deactivated.
Result: both tanks had the exactly same amount.
On a second test, I let it running for 60 seconds.
Result: the piped tank had 576,000L, which is exactly the listed pipe capacity: 9600L/sec.
The regulated tank had 578,400L, equal to 482mb/t ( or 480mb/t for 1205 ticks, which means that I took 60,25 seconds to close the valve).
This means that, while their medium output is about the same, there's a little difference on the frequency that they output.
I don't know if it's enough to affect the turbine functioning, but if I have time tomorrow, I might set two turbines to measure their total output (I probably will).