When do you use a chart in grouping games?

Hi!

I'm having a hard time distinguishing when it would be most helpful (and efficient) to use charts in grouping games. On the June 2007 practice test, I used a chart for game 4 - the recycling centre question and it worked for me but JD doesn't use it in his explanation video. I guess it did take me a bit longer using the chart, but I can't quite figure out the precise characteristics of a grouping game where charts would be most beneficial.

Help!