I use creative grids with the black and white lines. Easy to change the color for whatever fabric color is being cut. I also use the 6.5x24 inch ruler the most. It is my go to ruler. I flip the ruler depending on what I am cutting. One side has the 1/2 inch line down one side. The other side is marked in inches. You do have to be sure that you are cutting on the correct side of the ruler though.
Be mindful of the ruler and the size you are cutting. Use the same ruler throughout the cutting process to avoid discrepancies.
I also have the 6x24 inch ruler from Quilter's Select. It isn't my go to ruler. There is a new one that is 6.5x24 so I may try it.
Good luck on your ruler decision!