In what respect? Dynamic Lighting line blocking? If you mean distance.... they're exactly the same, provided they're matching corners. You can see exactly where the ruler is measuring from when you hold the mouse button down - you can set to center to center, or corner-snapping. Using center-to-center measuring for a full map/canvas size will give you a figure 1 tile shorter than the distance you want, but center-to-center is generally better for token movement, as you can't easily measure to the wrong place. Not without being a full tile out, which should be pretty obvious.
