The advantage of the x2vga2 over the 360 vga cable is that it would produce a brighter, more vibrant, less washed out picture when using it on a pc monitor. The main problem with the 360 vga is that the 360 produces 'Video levels' for colors, instead of 'PC levels'. The end result is washout colors with not enough contrast.
The disadvantage of the x2vga2 over the 360 vga cable is only 480p, 720p, and 1080i would be selectable resolutions (and 1080i would be out, because it looks horrible on a pc monitor), instead of the seven selectable resolutions that the vga cable offers.