It looks like the browser is enabling antialiasing on the 2D canvas by default. This has a high performance cost, so we have it disabled in the WebGL renderer. Instead by default Construct crops images with a 1px transparent border around them, so you get the same kind of smooth edge effect without the high performance cost of antialiasing. (If you just bucket fill and don't crop then you won't have the 1px transparent border, which is what I think happened in your screenshot with the Sprite, so try just hitting the crop button on that.)