This was exactly why I compared the two. If people are saying that sidewall skis give more edge hold than cap, this is good example to show how that is not the case because it"s so obvious. John said the same thing I did because it's an example we all know of- our race skis have been traditionally cap, with some exception. True we also have double deck on the Speed skis, but not on Slalom- there's no double deck on the World Cup SL skis, those are strictly cap.
Generally speaking, lots of companies (large and small) like to use sidewall skis because the manufacturer can change the lay up more easily. Flex patterns and weight changes are easier to make with sidewall construction than cap construction. This is only one reason why companies chose to make sidewall skis but it is super helpful when wanting to change the feel and flex of the ski.