What are the best practices for studying arial vs helvetica design history?

The best way to really understand Arial and Helvetica is to stop reading about them and start looking closely, because the differences are subtle and live in the details of individual letters.

• Compare letterforms side by side: set both fonts large and study the terminals, the uppercase R and G, and the lowercase a and t
• Look at terminal angles: Helvetica cuts strokes horizontally, while Arial often uses angled terminals
• Learn the history: Helvetica grew out of 1950s Swiss design, and Arial was drawn later as a metrically similar, license-friendly alternative
• Test them in print: print both on real paper stock, since type reads differently on screen than on the page

Once you can spot the tells at a glance, you will start noticing which one you are looking at everywhere, from signage to packaging.