A bit vague as there are (obviously) no exact numbers available, but public statements by the USAF suggest that the F-35's RCS is lower than the F-22's (at least from some aspects):
ORIGINAL: Air Force Magazine, USAF Generals Christopher Bogden and Mike Hostage
Hostage caused a stir in late spring when, in press interviews, he said the F-35 would be stealthier than the F-22, its larger USAF stablemate. Conventional wisdom had pegged the F-22, with its angled, vectored-thrust engines, as a stealthier machine than the F-35. Hostage also said the F-35 would be unbeatable when employed in numbers, which is why the full buy of aircraft is "so critical."
"I would say that General Hostage … is accurate in his statement about the simple stealthiness of the F-35 [with regard] to other airplanes," Bogdan said in the interview. The statement was accurate for radar cross section, as measured in decibels, and range of detectability, he said, and he scoffed at the notion that anyone can tell how stealthy an aircraft is just by looking at it.
ORIGINAL: Breaking Defense, General Mike Hostage
The F-35’s cross section is much smaller than the F-22’s, but that does not mean, Hostage concedes, that the F-35 is necessarily superior to the F-22 when we go to war.
I recognize that these aren't exactly exact numbers, but I thought it could be worth tweaking their RCS to reflect these statements. It's up to the devs in the end, of course, as it's not my game :)