The value of a fuel line isolator for safety is obvious.
The value of the gauge . . . I can see that you would want fuel pressure going to the data logger. Why do you need it during a run? I'm thinking you are pretty busy to even look at it.
What is the advantage of a mechanical gauge over an electric gauge?
The isolator adds complexity, cost, and another component that can break. Sure, the electric requires a sending unit that can fail, but wiring to a gauge beats plumbing.