Well, I think there are lots of reasons for EFTs . They're added versatility for all sorts of situations. I just thought the supersonic/supercruise bit was one interesting use of them since someone asked about EFTs and supercruise.
I think EFTs for Chinese stealth fighters, in the foreseeable future of China's security environment, would be limited in use to a rather specific set of circumstances (i.e.: jettisoning them once they exit friendly airspace).
Overall, they are versatile of course, and the primary means is via increasing range and/or endurance.
And yeah, to be honest I'm not exactly sure what kwaig's idea about EFT and supersonic flight really means