i think we forget something while we talk about these toys.
We shouldnt seek the best plane, we shouldnt compare them with eachother as if they will get in to a dog fight.(surely, russian planes will beat the westerns...)
The thing we need to compare are systems and strategies. Each country has its own air doctrine. if USA thinks JSF is good and capable enough to meet the requirements, if JSF will be enough as a multi role plane for air to air and for CAS, it means its ok. Somehow They will have other things to support those planes as best as possible.
Today's world is different than cold war era. The biggest threat against states are terrorist groups supported by other countries. Low asimetric threats play a key role in todays world. and countries shape their army organisations, logistic chains, doctrines and their defence systems according to these new threats.
Honestly, i dont expect a total war between any major country in Today's world. nevermind a war between russia and USA. if the thing we speak is quality and anti terror duty, The plane providing best close air support will dominate the market. also costs per plane is important.
Lets imagine the present situation of Turkey, what will happen if we intend to buy pak-fa instead of JSF?
at first we will be have to change the hangars. then we will re-train our support and maintenance units. we will be have train our pilots, some of the personal working in different sectors should learn russian for better co-operation with russians. and so on and so on... And most important thing is Turkey is a NATO member. and any nato member except greece doesnt buy russian systems.
So, a pak fa may seem the price/performance leader. but there are other expenses we should take in to consideration. only planes performance is not an enough to decide.
So what? nothing=) Western wing will keep using JSF and other old american planes, russians and allies of russia will use Pak-fa and other sukhoi models. Nothing will change, these countries will keep fighting in 3. countries, they will convert a 3. country in to a battlefield and decide on winner. ( please look at : Serbia, Kosovo, Bosnia, afghanistan, yemen, pakistan-taleban, india-mumbai, turkey, iraq, iran, russia-chechen war, saudi arabia, somali and so on...)
thats why i find comparing these two planes a little bit strange. They probably will never get in to a total war in next 30 years...