There are 2 things to consider when comparing them: 2 panel diffs and 3 panel merging. P4Merge is very good at the second but not so much at the first. Also,

There are 2 things to consider when comparing them: 2 panel diffs and 3 panel merging. P4Merge is very good at the second but not so much at the first. Also, to this date it doesn't have an OS-X version for M1 CPUs.