I've long wondered about that tradeoff: I've heard some (non-physics-aware) people say that heavier cars/trucks stop faster because they have more traction, but obviously there's a big tradeoff in that equation. As a guess, on a moving wheeled vehicle, 1 kg adds forward energy proportional to velocity, and downward energy constant and independent of velocity? And maximizing that tradeoff would seem to be an engineering goal in order to minimize muscle/gas expenditure. (I'm sure it's well-known but I'm too lazy to look up the details.)

That ignores road/tire and air resistance which are proportional to velocity. And I suppose a key question is the degree to which traction depends on vehicle weight: maybe it depends more on tire and road characteristics, for example. Certainly ice or some kind of low-grip tire would be a big factor.

And that ignores locking up the wheel, as you pointed out.