Efficient way of finding distance between two 3D points

Question

I am writing a code in C++ and want to compute distance between two points. Question 1:

I have two points P(x1, y1, z1) and Q(x2, y2, z2) , where x,

Answer 1

Is there a better way if I just want to determine if P and Q are in fact the same points?

Then just compare the coordinates directly!

bool areEqual(const Point& p1, const Point& p2) {
     return fabs(p1.x - p2.x) < EPSILON &&
            fabs(p1.y - p2.y) < EPSILON &&
            fabs(p1.z - p2.z) < EPSILON;
}