@Hazard - you're right, the MiG-25 in particular had a tube-based radar, which could handle far higher power than same-era solid state gear, which gave it the ability to burn through jamming at tremendous range (it put out 250Kw peak power IIRC) - and is EMP immune. One of the advantages T-50 has is its large radome combined with the recent availablity of gallium nitride transistors in the transmit/receive modules. The details (obviously) aren't out, but reasonable power/density/area assumptions give it a lot more heft that the F-22s APG-77. Also, the Russians have long experience with combined L/X band systems (at least as far back as Mig-31), and stealth doesn't work well against L band (L band, however doesn't localize as well as X band does). T-50 has this too.
Again, not to say which plane is "better". I haven't flown either one.