Think realistically. Benchmarks are fine for comparison, but show little real world results. If you've got a 1080p 60Hz monitor, like most of the world still has, it's not going to make a hill of beans difference if Intel gets 200 fps and amd only gets 150 fps. You get 60. It's minimum and average frames that matter far more than maximum ever will, and amd has a much better gap between min/max than Intel usually does.
So that leaves productivity, in which case means time. Ryzen wins most races there, even the 1st gen 1700 was double the speeds of an i7-8700k, that's huge time savings when compiling. Or photo editing etc.
The 9400's are decent cpus, IF all you do is game, and not too heavily. But if you do anything else, the thread advantages Ryzen offers is a possibility you can't ignore. You can't see 20fps difference when over 100fps, only a benchmarker can, and it's probably above the refresh of the monitor, so it boils down to a choice of adaptability or paper win.