So if it helps all this in any way here is my quick unbiased test using a challenging subject. I chose this one because it is a very high resolution mesh and also has a lot of thin tricky areas for auto re topo.
I ran Zremesher and 3D Coat Autotopo on default settings on part of one of the Crystal Palace Park conservation scans I am working on. I only have these two apps right now. Not Quad Remesher or current 3DS Max. This is without guides or density painting with just the base poly count taken up slightly to account for the complexity of the shapes.
They both managed it in very fast times. The Zremesher is the darker green and 3D Coat the lighter. The Zremeshed version was a more even quad flow, almost supernaturally so. The 3D Coat version is more spirally but seemed to also try to create poles or flows around some of the raised surface features. The Zremeshed version created a more uniform quad flow across the whole and kept the most straight edges across the thin areas like the tops and bottoms of the wings. But I think both results were fast and consistant in this test and could probalby be improved by tweaking the settings and adding guides.
As for 3D Coat. I have been trying out the manual re topo tools as well and loving R-Fill combined with quad loops.