Common guys, comparing the J-31 to any existing and deplored fighters is like comparing apples to oranges. The J-31 is a demonstrator and is still unfinished, while the J-7 is a mature and deplored fighter.
It's unfair to compare the J-31 to the J-7. A good analogy would be to compare a child still in school to a mature grown person with a job. No matter how brilliant of a student the kid is, he is still in training. Most likely, he makes no money whatsoever and still depends on his parents for everything even though he may be a straight-A student. The grown man, on the other hand, may be a janitor and makes meager wages. However, he has been tested in the real world and has demonstrated that he can survive the real world and can support his own family (no matter how poor of a job that he has done). So one can make the argument that the grown janitor is more proven than the straight-A kid.
However, we can all see that it is a very unfair way to compare the kid to the janitor. The kid is still in training and is in the process of improving himself. In other words, the kid is still in the "design phase". The kid has so much more potential. The janitor on the other hand is pretty much done for his life.
Other similar examples come to mind: comparing a baby tiger to a grown cat; a baby lion to a mature gazelle, etc etc etc. You get my gist.
For a proper comparison, you should choose players in similar stages of their maturity. How would the J-31 compare to the J-7 during a similar developmental stage?
The J-31's weapons launch system hasn't even been tested. So if you pitch the J-31 against the J-7 now, the J-31 won't survive. But does that mean anything at all? It's like pitching a 2-day old baby lion against a mature gazelle. The baby lion doesn't even have teeth yet. The gazelle can kill the lion cub in a second. Can you then conclude that gazelles are tougher than lions and can kill lions with ease?