On my machine, OpenGL generally runs smoother than DirectX, especially for games running in a window on the desktop. With DirectX, you always loose a few frames once in a while and get some tearing, even with no other programs running. With OpenGL, after starting up (10-20 seconds) the game just runs perfectly smooth.

Unfortunately, many people don't seem to have the right drivers installed for OpenGL, so if you release a game, many people may have trouble running it. Also, for it to run perfectly smooth, people need to enable the vsync option in their driver settings. This is often disabled by default.

Anyway, the Delphi/OpenGL example for Tile Studio can scroll perfectly smooth (here at least). It uses sub-pixel scrolling too, like the smoothscroll example, but a little more advanced

In the smoothscroll demo, there are very few tiles and most are always used with the same surrounding tiles to prevent problems at the edges. But normally, if you make a game using a map of tiles, you'll want to be able to place any two tiles next to each other without running into problems. In the Tile Studio demo, this problem is solved by having separate edges and corners for combinations of neighboring tiles on your map(s). For example, if you have tiles of 32x32 pixels, TS will generate new tiles of them (with the most often occuring edges and corners, 34x34 pixels) and some extra strips for edges with other tiles (32x2 and 2x32) and other corners (2x2).