Every situation is unique, and there are always a lot of variables. There are also a lot of ways to bi-amp (tri-amp, etc). Which is best is usually subjective, but typically if all else is equal an amp with less responsibility has some advantages over one that’s got a heavier work load.
How audible any improvements from a given bi-amp setup is also a variable. My experience has been that some scenarios are just subtle refinement, but some situations can be eye opening.