On the other hand, a heavy wheel will also hold more angular momentum and so will better resist drag, at the cost of more difficult acceleration, braking, and stiffer but more stable steering.
A heavier wheel, just like a heavier bike in general, doesn't "better resist drag". Yes, it makes the bike slow down slower, just as it makes it harder to speed up the bike.
When people say heavier bikes and/or wheels "resist drag better", it sounds like all that extra mass somehow magically makes it so that you need less power on the pedals to maintain speed. That is simply wrong.
No, it's not wrong. Given the same cross-section and initial speed, a heavier object moving through a fluid over a certain time will decelerate less than a lighter object, and so will require less energy to bring it up to the speed it had before decelerating, because the difference in speed will be less. For the same reason, you would not ride while dragging an open umbrella behind yourself, but you'd have no problem putting a metal cube of the same mass on your stem. It's the ratio of cross-section and mass.
> a heavier object moving through a fluid over a certain time will decelerate less than a lighter object
True
> and so will require less energy to bring it up to the speed it had before decelerating, because the difference in speed will be less
False
The higher inertia of the heavier object resisted the deceleration, and that same higher inertia will resist acceleration too in exactly the same way. You've gained nothing at all.
> For the same reason, you would not ride while dragging an open umbrella behind yourself, but you'd have no problem putting a metal cube of the same mass on your stem. It's the ratio of cross-section and mass.
Now you're talking about aerodynamics which is a whole different matter. For aerodynamics, cross-section is of course a major factor (not the ratio of cross-section and mass!). That's pretty obvious, but has nothing to do with a discussion about mass.
(Ratio of cross-section and mass is relevant for things in free fall, because there gravity is the relevant force. Completely different from a vehicle on a flat road.)
Drag will exert a constant force regardless of mass. So heavier wheels may allow you to coast farther, but at constant speed they don't affect the drag component.
I didn't say greater mass changes drag, I said it resists drag better. As you say, the force remains constant, so with constant force and greater mass, acceleration gets a lesser absolute value.
