MOTO Development Group, who carried out the test, tested the devices to see how responsive the touchscreens were when asked to draw a straight line diagonally across the screen.
While it's not something you do on a regular basis it allows anyone to evaluate the resolution and accuracy of touchscreen devices before they buy.
The result? The iPhone's touch sensor showed the most linear tracking with the least amount of stair-stepping.
The Droid Eris got second place with only faint wiggling – but actually performed best at the edge of the screen.
Last in the line-up was the Motorola Droid, which demonstrated significant wavy artefacts or "stair-stepping".