Difference in 10" brake drums

Someone else will chime in more accurate. I have read that there are special bell-shaped drums, like the one on the left. Save it, people crave it. It is "correct". I always figured a regular full-width drum, like the one on the right, should work fine as long as the "snow lip" sits the same place relative to the backing plate. You just have more width for the shoe than required. Seems somebody else figured that and it does work.