The 55gr Nosler Btip gave me more runners and floppers than I cared for, and I even lost one. Last I saw of that coyote he was running up hill, with either skin or internal stuff flapping out of his side.
I have often wondered if I had a bad batch of that bullet? I really liked the speed (4,000fps) and flat shooting of it (200yd zero, 12" drop at 400yds), so I may try it again next season.
The 75gr Vmax has performed great, with very few coyotes getting damaged. The ones that are damaged, are severe.
This year, I am using the 70gr Btip, and, so far, good, consistent results, i.e. bang-flop.