Needle nose gar (Xenentodon cancila, just to clarify we aren't reffering to longnose gar) are delicate little fish that stay small, have no protection, and no bite force. Torpical gars, like most gars get big, are covered in armor, and have serious jaws /teeth. I'll let you conclude what will happen when the two get into a scuffle (or more accurately, when the true gar chows down on the false one)...
On the other hand, one one is about a hundred dollars more valuable than the other...