Here is what is going on in your scenarios:
Coasting in neutral: The engine is running at idle, the gears in the transmission are disconnected from the drive shafts (the drive shafts being what connect the transmission to the drive wheels, which are the front wheels on your Honda). The engine and transmission are suffering no more wear than they would were the car stationary.
Coasting in gear: Your foot is off the accelerator, so (assuming your Fit has a gasoline engine) the air supply to the engine is nearly cut off and it is burning little fuel. It "wants" to spin at idle speed (approximately 1000 RPM), but because it is still connected to the transmission by the clutch and because the transmission is in gear it is being forced to turn at a speed that matches the current gear ratio and speed of the car. The engine is acting as a brake in this scenario, which puts slightly more wear on it and the transmission than if it were disconnected by pushing in the clutch pedal or putting the transmission in neutral.
Coasting in gear will put slightly more wear on the drivetrain, but not a harmful amount. Indeed, sometimes a driver will deliberately rely on the engine braking effect on a long downhill section of road in order to avoid overheating the brakes. The lower the transmission gear the stronger the engine braking effect and the more wear on the drivetrain.
Assuming you were up to cruising speed at the top of the hill and therefore in a high-ish gear, coasting down the hill in that same gear won't hurt anything. I think the difference in wear will be negligible. Which is more fuel efficient, I'm not sure.
A related point: leaving the clutch disengaged while coasting (that is, keeping the clutch pedal pushed in) will accelerate wear on the
clutch throwout bearing (credit: comment by @Ukko below). If a driver is going to coast, I think marginally less wear is suffered by shifting to neutral then re-engaging the clutch (i.e., releasing the clutch pedal). However, the extra wear may be negligible on current cars; see @Ukko's comment to this answer.