Rafales are considerably more expensive - India paid like $250M+ per unit (and lost like four of them to F-16s/J-10s). F-35s are $70-100M. Imho F-35 are superior in this scenario due to its stealth features - they'll be operating very close to russian AA systems
The F-35 is expressly vulnerable, in this scenario. If Russian radars were the only threat, you'd be correct. The MiG-31 has a top-notch IRST system though, they can get a missile lock on the F-35 regardless. "Going dark" is pretty much useless for this scenario.
For a pure interception-style mission profile, an F-15 or even F/A-18 would perform much better. A Rafale or Eurofighter platform would also suffice. The F-35 is a Joint Strike Fighter though, and I think people forget why it was made. It's a bomb dropper, the F-16 will outperform it in a one-circle and two-circle engagement. The F-35 is just not built to dominate air combat, and that's okay. It only becomes an issue when customers don't know what they're buying.
What is significance of having a passive relatively short-range sensor for violating aircraft in this scenario? Nothing on mig-31 is "top-notch" - it's 50 year old tech. Even Zaslon-M probably isn't capable of detecting F-35 with its low RCS beyond 50mi
I think you're discounting the MiG-31 in this engagement a bit. I like the F-35, but it was only going to be useful here if they fired an AMRAAM. They didn't - the F-35's radar and datalink advantage was never used. It never intercepted the MiG-31s or attained visual identification.
Let's start with this, Russia knows that NATO fears escalation. As long as their MiGs don't open fire, they can maintain an ambiguous international stance (even if they were definitively wrong). SAM operators would hesitate to open fire; in training they learn that modern decoys can spoof RCS and potentially endanger civilian aircraft in the confusion. So, they raise the issue with their allies and see if a response can be scrambled to deter further airspace violation. Assuming Russia never intended to escalate, this is the point in their plan which they bail out.
You're correct that Zaslon is largely useless here; the IRST is much closer to SOTA and well-integrated with the R-77 and R-73 missile family. These are pretty demonic missiles if you're a stealth aircraft, and they can be queued off-boresight to deter anyone from wanting to get close: https://youtu.be/a6TiPNW512g
I agree that if the goal is traditional cold war era intercept ie show of force then rafale is probably better. Not sure if that strategy will be effective here though - vks seem to pursue different goals here
