I thing the Lightning role counterpart variant would be the MiG-25P, and by their nature there would never be an encounter between them. Maybe with an RB. No guns on either, I think. R-40RT/TD missile was a bit of a monster but on an airframe like the 25RB I'd rather have R-40 than R-60: the latter would commit the plane to a dogfight it couldn't dominate. Also, R-60 entry was past Lightning's end-of-life, I think.
But in a synthetic Lightning vs MiG-25P fight with both starting either on the ground or at altitude beyond detection range, and the same pilot in both cockpits, I'd go with the -25P.