There is no species of gar that is generally nicer than the other. If you want a true gar that is easy to care for I would recommend the Florida Gar Lepisosteus platyrhicus due to them being one of the smallest gars reaching around 20 inches in the aquarium. They generally will not nip or bully the other fish but they will eat any fish smaller than 2/3 of the gar's body length if it is hungry enough. If 20 inches is too big for you, then you could probably get away with getting Either the Striped or Spotted Pike Characin Boulengerella lateristriga and B. maculata, the Hujeta Pike Characin Ctenolujus hujeta, or the Asian Needlefish Xentodon cancilla. Each one of these fish are commonly sold as Marbled gar, Striped Gar, Boulengerella Gar, Rocket Gar, Slant-nosed Gar, Needlenose Gar, and Asian Gar, but they are not true gars. Each one of these fish will reach a maximum length at around a foot long, some getting slightly larger. Hope this helps!