How does one decide which type of seasonal (average or link-relative) to use and when?

Let's first look at a 10-year March Corn seasonal made using the link-relative method as shown below. The first thing to notice is that there are two vertical scales: one on the left with units of the open contract (C2010H) and one on the right for the seasonal with units of percent. This allows the graph of the open contract to be overlayed with the graph of the seasonal. Notice that the seasonal (with standard deviations) fills the chart making it easier to read. But while this chart is great for seeing whether the TREND at any given time of the year is bullish or bearish it does not show how the LEVEL of the current contract compares to the historic level.

To see the historic level we need to look at the same seasonal made using the average method as shown below. Since the units of the seasonal are the same as for the open contract there is just a single vertical scale. We can see that the C2010H contract is about one standard deviation above it's 10-year average.

I'll be adding more soon so be sure to check back.