There's a tremendous amount of very detailed information on the F-35 and its potential adversaries on the ausairpower.net site. I'll warn you in advance they are no fans of the F-35. However when you take a look at what the PAK-FA puts on the table in terms of sensors (IRST, 360 degree X band AESA, conformal L band, LRF), weapons (TV and GF multispectral missiles), performance (Mach 2+, 3D thrust vectoring), and it's own stealth - you can see the the F-35 is not even in the same category.
Of course, it shouldn't be in the same category. The F-35 is a strike plane, not a fighter, and is designed to operate in skies swept clear of opposition by the F-22. PAK-FA is designed to take on the F-22, and does it with technology 20 years newer than the Raptor. L-Band and IRST are both stealth-immune, and I'm sure I don't have to tell anyone here about that Sukhoi leads the world in BSM and TV for the close-in fight.
Any nation that buys the F-35 is going to have to accept that Venezuela and Vietnam will be flying better planes.