Thanks for the numbers. It basically affirms my estimate that the F-18 has a relative RCS advantage against the J-15 by at least 5 X.Take these with a grain of salt (CMANO db). Frontal aspect rcs:
It's well known that the Rafale has extensive LO measures implemented and it should be no surprise that it is the "stealthiest" of the three. Having said that, as Tam pointed out, aircraft RCS is highly dependent on the illuminated CS and loadout. A proper comparison (with access to classified data) would take space and effort of a master thesis.
Btw, you are right in an earlier comment that there is a relationship between RCS and jamming power requirements. A lower RCS platform has a jamming advantage in terms of power requirement.