BrepFace Split brep inside Curve

Maybe it´s a silly question but I´m stuck.

I´ve made this

Brep brepSplit = brepFace.Split(contornoSplit.DuplicateSegments(),                                                    RhinoDoc.ActiveDoc.ModelAbsoluteTolerance);

This generates a brep with 2 faces:

Now, I want to select the face inside my cutterCurve

But I don´t know how to differentiate between the two faces which is what is inside the cutting curve.

Try comparing the bounding boxes centre point of the two faces with respect to the bounding box of the curve. The distance will be different, and you need the one with the smaller distance.

I see a problem with this solution, if match the getboundigbox centre point, for example, it the cutter is in the centre of the Brep