I have come to the conclusion that voltage amplifiers are better than charge amplifiers.  Equations state that the gain should be the capacitance of the hydrophone divided by the capacitance of the integrating capacitor.  When creating two circuits with (about) the same gain, the voltage amplifier always outperforms the charge amplifier.

This could be because of a few things.  Firstly, the capacitance of the hydrophone stated in the datasheet may not be true, or the capacitance undesirably alters with frequency.  Or secondly, it could be because the hydrophone, as a model, is a better voltage source than it is a charge source, however this is implicitly the same thing.  I.e. When the structure of the ceramic changes, a charge is formed via electrons jumping into non-stable spaces.  This forms a potential between the terminals on either side of the ceramic and when one side is connected to ground and the other to a load, a current flows.

So, in reality, for hydrophones at least, the two circuits are attempting to accomplish the same thing.  However, I would be worried that the integration in the charge amplifier would cause the signal to be altered from the delta like pulse to some sinc wave; single-handedly demolishing the drop size-impact pulse relationship.

Feel free to correct me if I am wrong, and here are some images of the results.  The charge amplifier simply didnt have enough gain to get the required results.

Incidently, a differential configuration did not work very well at all.  I thought a differential amplifier would remove a lot of the mains noise, but it didn’t.  Most of the mains must be picked up in the actual circuit, rather than the wire.  To remove the noise I would have to use a DC servo, adding complexity and possibly more capacitors in the path of the signal.