My choice would be the Yachtsman Steakhouse. The worst of the bunch would be Brown Derby. Last month 3 (filets) out of 6 meals were inedible and the other 3 were just okay.
For what it's worth, in my opinion the "signature" designation is simply a marketing ploy to promote what used to be good restaurants prior to the designation. While a few are still holding their own, many are disappointing.