It is a legitimate question that is difficult to answer because there are little to no examples from actual warfare. What would happen when two pilots fight for real with $100 million aircraft on the line? It's hard to answer this definitively.
A lot will depend on the combat context. Are we fighting over the ocean or in a big mountain range, like the Caucasus or Carpathian mountains? If it is useful for an aircraft to hide in the mountains, maneuverability can be extremely important.
Speed is always very important because more speed increases the ability of the pilot to position the aircraft in a favorable location preliminary to the engagement. In exercises this matters less because both aircraft are placed in neutral or "equal" positions. In real combat usually positioning is unequal and whoever can get to the good spot first will have an advantage, often a decisive advantage.
Firing a missile at someone you cannot see is problematic because how do you know they are the enemy? Also, they can see your missile on radar way ahead of time and evade it unless you get sufficiently close before firing. In real combat the enemy will not loiter out in the middle of the wild blue wonder just waiting for you to come and shoot at them. They will always position themselves in a secure location, such as close to the ground, where you can't see them.
The defender will have a huge advantage if they have ground radar or an aerial radar, such as one on an aerostat, because they will see you coming and they can position their aircraft to ambush you. This is why SEAD is so important. Against any opponent that has anywhere near your capability, it is suicidal to act due to the advantage fixed radar will provide. In a future war it is likely that specialized antennas will be made that are distributed and difficult to destroy. This will make aerial attacks on foreign soil very difficult, unless the enemy has primitive technology.
As far as the design of the T-50 is concerned, the focus on maneuverability is reasonable, especially for a defensive, air superiority fighter. As far as aircraft radar is concerned, be aware that it can only see (at best) in an 120-degree cone directly in front of the aircraft and if you use it, you light yourself up like a Christmas tree and everybody will know exactly where you are. Therefore, in a real war aircraft will, in many situations, not even use their radar, because it will give away their position, thereby allowing an enemy to pop up behind them and shoot.