Mandarin and Scooter Dragonets
Appearance
Mandarin is larger, more massive, and elaborately colored, and scooter - more elongated, slender, urban camouflage colors with cherry red strips on the fins. Both look full bodied, not slender, when are well fed. See thephotos on the side bar.
Colors of mandarin
Now about so called beautiful colors of mandarin: it reminds me most of the male betta fish - the same passive dullness. More like mourning colors of the tank, paired with the lack of personality. If yours is different - good for you.
I still can't figure out, under what conditions the mandarin can look colorful. Most probably, when excited, and this is not a frequent occurrence. The second probability: it may reflect the bright light, or the light passing through the tail fin, makes it looks bright. If the clownfish has bright, light independent color, and the chromis - reflected, different under different angles, but still always colorful, the mandarin is dark and dull even directly under 55W PC lamp.
Now the best part: colors, when excited, "driving the enemy out" sequence, the same place. 
This lasted seconds, then mandarin relaxed and turned his back to the potential enemy. If the problem can't be solved, it better to be ignored. Something like that. Classic standing on the tail (hovering, actually), for a much longer time. The second mandarin, in another tank, was doing precisely the same.
Appearance of the scooter
It's easier: the same color all the time, except when becoming pale during the sleep or trying to make itself invisible before the enemy (the same sex of own kind, alas).
Movements, or manners
When not harassing the younger fellow, the mandarin's movements are delicate and graceful. Scooters are more straightforward, fast and energetic.
Next page: Personality and compatibility