Chest and hopper minecarts lose almost no speed.

I can confirm this. In a test I performed, an unoccupied minecart traveled 7 blocks, one with a hopper traveled 66 blocks, and one carrying me traveled 94 blocks (without using boost).

Confirmed.
The TNT, furnace and regular minecart travel some 6-7 blocks when accelerated with one powered rail.
The hopper and chest minecart travel quite far (to the tower of hoppers in the screenshot)
It's not a matter of weight since hopper and chest were unloaded.

May be intended: https://twitter.com/Dinnerbone/status/298541610491342849

My test was done with empty chest / hopper.

I know, but this may be so that a heavy cart goes as slow as a player cart, etc.

An empty cart runs way farther than a fully loaded cart. This may be inverse logic as intended.

I believe it works as intended. Minecarts carrying empty containers have less inertia than a minecart carrying a player. Empty minecart are the exception, slowing down faster to prevent them from going wild and forcing players to run after them at the first occasion.