Pretty sure if BJS had been dedicated to his craft for his entire career he'd have campaigned largely at 154 and moved up to 160 round about now. He's not a bone fide SMW. Plant - although less skilled - is a genuine 168 fighter. If they fought now, I'd favour Plant...
Even though his eye is shot, I still think Saunders is slick enough and has enough to beat Plant. Although I'd fear him getting robbed if the fight were held here. But stylistically, the fight definitely favors Billy Joe. I can't recall Plant ever facing a southpaw and it would force him out of his comfort and into taking a more aggressive active role, and I don't think that's a role he's ever been comfortable in. Saunders would just lay back, make him miss and pick him off as he comes in like he was doing to Canelo for the majority of their fight, that yes, he performed far better in than Plant.