I think it would be wiser to use "Every X Milliseconds". Assuming you have V-Sync enabled, "Every X Ticks" could produce different results on different computers, because 1 tick is equal to 1 frame.
For example, if you have a monitor refresh rate of 60hz and setup your game accordingly, anybody who has a different refresh rate -- for example, 75hz, 80hz, 120hz, etc... -- would run into the problem of the video looping before it's even over.
Using "Every X Milliseconds" would remedy this. Plus, finding the amount of milliseconds would be just easy, if not easier, than finding the amount of ticks.