Line on the Ball
Should you use a line on the ball? Well, that depends. How well do you aim your putter without a line? Do you see a curve on the green where you see the putt breaking? When you use a line does this negatively impact your distance control? Are you a fast player or slow player? Does your putter have a line on it extending to the front edge of the putter?
If you don't aim your putter well without a line, using a line (correctly) will almost assuredly help you line up better. Best practice is to use a longer or extended line on the ball as a direct connection to your line on your putter in order to line up correctly. Suprisingly, I've seen hundreds of players use a line on the ball, but then not be able to properly line up their putter in a way that the line on the putter and the line on the ball are in unison. Having a gap on the top of the putter with a line only on the bottom of the putter for some reason doesn't work well with many players, as that 3/8" of blank space doesn't make it easy.
Many players perceive a curved line on the green where they intend to roll the ball. Those that see this curve are called non-linear. Linear players don't perceive this curve and tend to putt at a spot or inches outside the hole or items in the distance. Non linear players may have a hard time adjusting to a line on the ball, but you can try it and see if it works for you. Linear players typically adjust well to a line on the ball.
If you like to play fast, keep in mind that using a line will likely slow you down. Keep in mind that this could negatively impact your putting as we all need time for a solid pre-shot routine and to not feel rushed when putting. Some players also get line concious and have worse distance control when using a line.
So the answer is not one size fits all. Be aware of the above and give it a try. Many College and Tour Players are using a line on the ball. When they have decided not to, it's most likely due to one of the reasons above.
Andy Thompson