Is there any big difference between the J11 and SU27 or is the J11 just a copy?

I was recently wondering what tree in air i should grind and based a lot on looks i love the way the SU27 looks (allready got the mig29 from germany), so i was interested if there was any big difference between the SU and its chinese version the J11

The J-11 ingame is an Su-27SK, IRL it has a few downgraded features, but ingame its basically identical (sans being like 500kg heavier but it doesnt have any real effect ingame).