Let me ask the right question.

What good is the DCTI if you have 2 WPS500s connected to 2 channels of the scope?

I don't understand the question Sam?
What are you asking ?

Sam,

If you have two WPS then you can do the dual channel pressure thing same as the DCTI.

The WPS would also be more versatile and capable of measuring lower pressures and pulses with more resolution.  The DCTI cannot do exhaust pulses for example.  The WPS can.

The only other thing about the DCTI is that you can also attach other probes to it besides transducers and utilize the DCTI filtering.  For example, you could attach a noisy amp probe and filter out the noise.

This is less of an issue with Pico, since it has software selectable low pass filtering anyway.