Chengdu's aircraft looks like it is capable of internally carrying large standoff armaments up to 6m long. Probably PL-17 and anti-ship cruise missiles. It does not appear Shenyang's aircraft will be able to do the same. Shenyang's looks smaller, and powered by only 2 engines. Also, its inlets appear to take up valuable space on the underside. There's just no way Shenyang's aircraft can accommodate an oversized weapons bay like Chengdu's.
I think Shenyang's aircraft is more of a traditional multi-role fighter. Chengdu's aircraft is more like a supersonic missile truck built to carry large standoff missiles. I don't believe they are competing with each other.