Quick answer. KWA is the no-trademarks and lacking the trigger safety version of KSC. KSC's have trademarks, the trigger safety and a slighty higher Quality Control check. Otherwise they're the same thing.
KWA's also come stock with a metal slide/outer barrel where KSC's will have a plastic/abs slide.
I'd suggest doing some more searching on google for reviews of each if you're really interested.
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Various BB throwers
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