I have seen many people throw both balls. I have thrown the Frantic and like others here have found it to be very over/under. Could be my stats.
But ultimately, I feel the two balls are too close to one another to warrant having both. That is unless you just want to experiment or are looking at eventually replacing your current Frantic. The only reason I could see needing both would be on difficult shots where the small amount of difference may be needed. But THS are VERY forgiving and if the Frantic is too much, I would have a larger step down than the Wrecker.
With all that said, the Wrecker is a wonderful ball and if you decide to get one, you should enjoy it.