Answer: The less massive object because it interacts with the Higgs Field less than the more massive object
Step-by-step explanation:
There's a simple and very good explanation of this. The Higgs Boson particle is thought to give things mass. And all objects with mass move through the Higgs field interacting with the Higgs particle. The most massive object will interact with these particles more. Therefore gaining more mass. Which in the end makes it move slower. This is actually why objects with mass can't reach the speed of light.
And a good analogy that Neil Degrasse Tyson used was a celebrity entering a bar. People will crowd the celebrity and the celeb will have a difficult time moving around. On the other hand, a simple nobody will have no attention and move around pretty quickly.
Fame = Mass
Ability to move around = How they interact with the Higgs Field
I know this wasn't the answer you were looking for, but it is something to keep in mind when doing future problems in physics