Hello ekerazha,
The differences lies in the detail. So the S-Flex has a rotor suction magnet. There's an extra magnet that keeps the rotor in place. The IC used for the control of the fan is also a low noise IC. Thats something the Kama Flex doasnt have.
I hope this helps you a little bit.
Kinf regards
Chris - Scythe EU GmbH