Not sure how helpful a visual demonstration would be, but guide number differences certainly aren't a very useful comparator.

If it helps, the 600EX-RT has light output that's ~2/3-stop greater than the 430EX II. So, if you needed ISO 640 with the 430EX II, you could use ISO 400 with the 600EX-RT, or if you needed f/2.8 with the 430, you could stop down to f/3.5 for a bit more DoF with the 600.

Lots of other useful features on the 600, like better head rotation, the catchlight panel, weather sealing, etc.