>>38471403In all fairness he DOES have some edges over Gyarados. He's not x4 weak to electricity, he's not weak to stealth rock, and he has better physical bulk than Moxie Gyarados sets. His move pool is also greater and thanks to Sheer Force, he does more damage with his non-stab options. For example, Ice Punch with Sheer Force gives the gator a 97 base power Ice Move, while Gyarados is stuck with Ice Fang. AND Gator can use a Life Orb to power that punch up without any recoil. The same applies to other non-stab options as well. Plus, he has Liquidation, which is powered up further by Sheer Force for a pretty impressive base 110 powered move.
Don't get me wrong though these are all narrow advantages. Gyarados has higher base attack, Intimidate for more immediate physical bulk on a switch in, the flying type to avoid other entry hazards like sticky webs, higher base speed and special bulk, and the option to use a Mega Stone to switch out the flying type for a Dark type with Crunch and Mold Breaker + Taunt to stall kill.
Feraligatr has some things that Gyarados can't do and has it's own unique niche but it's never seen in OU just because Gyarados exists. But just because it's overshadowed doesn't mean it's bad. If you need a D-Dancer with Water Stab who doesn't take a mega slot he's a good option. Gyarados fits more holes but there's somethings the gator can do that he cant'.