KWA / KSC are basically the same guns. KSC are made in Japan, have full trades, and come with ABS slides. KWA are made in Taiwan, have metal slides and no trades. So basically the same gun.
However, the PTP are different guns completely. While they're the more realistic guns, they're also more expensive and have been reported to be more problematic (at least the 1st generation) than other KWA guns. They're not compatible with other aftermarket parts and incompatible with any other magazines, and PTP mags are hard to come by.