As usual, the line to watch is the thick green one, which should have less variability than either individual index. (Both indices are extreme-adjusted, but that mostly just reduces the down spike caused by covid in 2020.)
Right now, the manufacturing PMI index is rising while the manufacturing ISM index is falling. This divergence in direction hasn't happened before. In 2017/18, a gap between the levels of these two indices did open up, but their direction was roughly the same. But since late 2025, the PMI has been rising, while the ISM has been falling.
Which is "correct"? We won't know for another few months. What we do know is that the average of the two is flat, and only just above the 50% "recession line", in other words, stagnating. If you feel compelled to go with the "better" index, that's prolly the ISM*, which goes back to 1947, when it was called the NAPM* index. It has correlated well with every major and most minor business cycles since then. And it looks as if it's falling.
*NAPM = National Association of Purchasing Managers. ISM = Institute of Supply Management. I suppose they thought that sounded a bit grander.