As far as "factory production calls" go, I'm a big fan of the Randy Anderson Primos calls, the Double Cottontail is the best closed reed factory call on the market in my opinion (as a collector/obsessor of predator calls). The howlers, Hot Dog and Lil Dog, aren't great, but they're about as good as anything in the factory call market, 2nd only to the Dan Thompson howlers.
The Flextones in general, there's nothing "wrong" with them, but nothing that makes me want to recommend them to anybody like I might recommend other calls. I personally think if you throttle them much (squeeze the bell), they sound like a dying rabbit underwater. In my experience, I lean towards harder materials to get better sound and better volume out of closed reed calls, like Acrylic, aluminum, horn, or antler, so these soft rubber calls are goin the opposite direction from what I want in my calls. Your mileage may vary. There's nothing wrong with the Rabid Rabbit except that they copied Kerry's name!! (I don't care which one of them came up with it first, it's KERRY'S!!!)
The flexible bell/bodies deal is kinda a gimmick to me. I have better control (read: I'm well practiced) using my hands/side of my finger over the end of the bell to change the pitch of my calls, so I just don't see the benefit in bending the rubber calls. Again, your mileage may vary.