What are the techniques employed when showing quantitative differences between Bar and Column charts?
To begin with bar and column charts are the same type of chart, just different names. Second are you trying to show quantitative differences within one chart or between two or more charts?
If you are trying to show differences within one chart, then you can use different colors or shadings for the bars. For example a bar representing women could be red or have polka dots in it, while a bar representing men could be blue or have squiggly lines going through it.
If you are trying to show quantitative differences between 2 or more charts then you need to be certain that the charts have the same scales. It would be very distorting if one chart went up by 10s and another went up by 1,000s. Second, it is easier to compare two charts if they are side by side, or at least on the same side of a piece of paper, as opposed to being on opposite sides of the same piece of paper.
I hope that this helps.