Originally Posted by Fat Lucchini
Furret has 76 base attack, 4 points lower than Miltank's base, so I feel you may judging Furret by its competitive usage (where it shouldn't appear besides joke teams) rather than what it does in-game. Furret (caught earliest as Sentret and trained) and Miltank at the same levels (which doesn't happen in practice because Miltank is pretty underlevelled when you can first get one) should have around the same firepower, Furret possibly more depending on how many Pokemon providing attack EVs you fought on your way (which could be a lot knowing you've passed three gyms and five towns). Furret also beats Miltank in availability, and has powerful Return as a result of being around for so long, not to mention Dig and Shadow Claw access for coverage which Miltank lacks.
Furret's rather poor at taking hits though, but not entirely bad with 85 base HP and just average defensive bases.
Factoring in Furret's superior availability, I'd say he and Miltank are about equally good for in-game purposes. Furret might be OHKOing more for a longer period of time.
Seconding this; Furret trashes Morty with the conveniently placed Shadow Claw TM just outside Ecruteck, and hits pretty hard for a good chunk of the game. Mid for sure, just like every other Generation Rat in our tier lists. Granted, he's no Raticate, but Raticate can't very well hit Morty now, can he?
Also, Gyarados isn't as tedious to get as Lapras is; swimming to the middle of the Lake of Rage is nothing compared to backtracking to Union Cave and spamming Repels to get Lapras. That should definitely be a plus for Red Gyarados.