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ELI5: Which cyclist gets down from hill faster, heavier or lighter?

Hello, 
What I'm asking is that we have 2 cyclists, with same bikes, going down same hill. They only go as fast as they can without pedaling. 
Which gets down fastest and why? How inertia affects velocity comparing both of them? How friction affects them considering heavier cyclist is also bigger in size? 
I'm asking for as deep explanation as possible, please. Any equations would be appreciated aswel.
gpt
Inertia is irrelevant, since the force making them move depends on their mass.

Friction between the bike and the ground should also be equal, since it's ideally proportional to the force pulling the cyclists towards the road surface.

Basically, in a vacuum, both cyclists would move at the exact same speed at the same time.

However, friction between the cyclists and air doesn't depend on their mass, it depends on their shape and size. The interesting thing about this is that the size does not scale proportionally with weight. Doubling the weight of the cyclist would roughly increase his size by sqrt(2), about 1.41. So while he is twice as heavy and therefore pushed forward with twice the force and experience twice the rolling friction, he is only slowed down 1.41 times as much as the lighter cyclists due to wind resistance - which means that he will eventually move faster and arrive first.

It is for the same reason that large passenger planes require less fuel and have longer range than smaller planes: They require less thrust per ton of weight to move at the same speed.