The actual draft instructions for either cap sleeve are fairly simple and easy to draft. Even so, I didn't like the shaping and resultant styles of either sleeve. I'll try to explain the differences of each. I had a stronger preference for the Armstrong version, but I still modified hers considerably.

The top sleeve is the Aldrich version, the bottom my modified Armstrong sleeve. The Aldrich sleeve is very straight - such a sleeve results in a large sleeve cuff opening. Her sleeve is not a fitted cap sleeve. The instructions were easy to follow, I just had a styling disagreement.
I much prefer a fitted cap sleeve. The basis of the sleeve draft must start with a regular sleeve block. Just draw in a style line similar to what you see in the photo for the shaping at the hem. There are some minor refinements detailed in the Armstrong book. The problem with the Armstrong draft is that the sleeve cap height was too high for a toddler. I decreased the cap height by about a good 1/2". Walk the sleeve cap along the armscye and adjust any length differences. Armstrong states there should be 1-1 1/2" of ease in the sleeve cap, which is simply too much. My sleeves have virtually no ease because I removed it. Sometimes the fabric calls for 1/4-1/2" of ease, but not anymore. A sewing operator will return a bundle with too much sleeve cap ease. It is just too difficult to sew in an industrial sewing. And in IMO, it doesn't do anything for fit or wearing ease. Armstrong's draft instructions are easy to follow and you can make any adjustments you prefer after you have the shape you want.
If you look closely, you will notice that my sleeves are symmetrical. This is because my bodice armhole shapes are identical for the front and back. This is typical in the industry for infant and toddler styles. In older children, this is not true and Aldrich's basic sleeve drafts illustrate the differences very well. Kathleen Fasanella has blogged much on the proper shaping of sleeve caps.

Either book will get you a basic cap sleeve. My eyes prefer the fitted style. Any questions? Anyone need draft instructions?