I don't know what Construct does for "motion blur", but if it's in any way realistic, then the higher the frame rate the less motion blur you get.
That's right - Construct's motion blur is effectively a sum of everything that happened since the last frame. The higher your refresh rate, the less blurry things will look - but it usually makes motion look much nicer even at high rates! Motion blurred graphics are much more pleasing to the eye - your brain can make sense of how fast things are moving, and in which direction, from a still image.