Might be nice to introduce yourself.... anyways welcome to S101. Biggest difference - in 6 color it will print about half as fast. NO (yes NO) additional color range is provided by going to 6 color, just almost imperceptably smoother transitions in skintones and some gradients. Over the past 10 years or so I have only met a couple of people who did not ultimatley change their 6 color setup to dual 4 color and never look back... unless of course it's a machine that does not support dual cmyk.