k, they still make faulty ones that swim better than the 'good' ones, because i just got some new ones. You are looking for a straighter edge on one side. most tadys look like this: (). you want the ones that look more like this: (].
Wow i dont know if that makes any sense to anyone out there but if you think about it thats what it kind of looks like. Its just a missed shapen one that has a straighter side than normal. this causes it to flutter and kick a little bit different with a little more action. try it out it will help.