Both of these eels will get very big. The chain may stay a little smaller than the dragon, something like 2.5 feet compared to 3 for the dragon. As far as aggression goes, all eels are somewhat aggressive, but usually not overtly. They will try to eat anything they can fit in there mouths, but won't mess with much else unless there are provoked. Either one would be a good choice for an aquarium of 125 gallons or more. I personally think the dragon eels are better looking, but they are more expensive.