I suspect most will probably pick Rios, but I dont see it that simple. People act as if Judah was some type of scrub. I'd pick the pre-Tszyu Zab over Khan, Bradley, and Alexander without thinking too much about it. Maidana might have blasted him late, but Chino could have also been blasted out mid rounds. And prime Zab would have destroyed Victoria Ortiz. Rios would essentially be faced with Acosta times 2 or 3 against a prime Judah. He had trouble with Acosta's speed early, and was stunned by Acosta's power. In Judah he's faced with FAARRR more handspeed than Acosta, better power, and yes.. prime Judah was also a more elusive target than Acosta, and a southpaw. Could Rios grind Zab down, and stop him late? Sure, its possible. But its just as possible to me that Bam Bam, with his lack of regard for D, walks into something big he doesnt see and gets starched.
Judah is always tough to pick fights with. To me this is a 50/50 fight. There is an equal chance of Zab frustrating Rios, then hitting him with a few massive shots and KOing him as there is to Rios simply grinding Zab down, making him fold and KOing him as often happens with Zab.