Not much. Writers, artists and editors migrate back and forth between the two companies and this has been true for decades. Their style of storytelling are pretty similar as well. Marvel hasn't been the hip and cool upstart since the last Century. And DC stopped being "your grand dad's comics" around the same time.
Marvel's ballyhooed "rich wealth of continuity" and "evolving universe" is just as confusing and convoluted as DC various reboots. "One More Day" and even the "Winter Soldier" are as damaging to continuity as any Crisis at DC. In the end its about telling a good story. Frankly slavish continuity doesn't always make for good storytelling. It can lead to a lot of wheel spinning and backtracking when moving forward should be the goal.
Worrying about what happened and didn't is just silly. I can't get into that mindset anymore.