In your meter options, you can select segmented or non-segmeted.
Segmented meters are less CPU intesive, so things run more smoothly. This is because by segmenting them, they have a lower "resolution" and hence a lighter load on your CPU.
Also, some people like the way they look, and others are more familiar because they resemble a hardware console.
All in all, if your CPU is not being over-taxed, it's just a matter of preference. I find the non-segmented meters to be easier while mixing because of the better resolution, and I like the way I can change the color.