Until pretty late in his career Simon Brown had a pretty sturdy beard. And he has the strength and skill to beat Cuevas. I will go with Brown by decision.
Brown was durable, as others have pointed out. That said, Pipino hit hard enough to break bones. Randy Shields was able to stay out of danger for fifteen rounds, so Brown probably could as well.
Brown's best WW victory was probably over Maurice Blocker for the unified WBC / IBF title: “Yeah, my trainer [former welterweight and middleweight champion] Emile Griffith told me that I have to stop him because I was behind,” Brown acknowledged. “Once he told me that I had to go to for broke and stop him and that’s what I did via late TKO. (Brown goes to war with friend and foe, Maurice Blocker.). The next day the two families went for dinner together and later, in an unheard of gesture, Brown would vacate the IBF title he’d held for years as a favor to the man he’d conquered. “I did that because I wanted to give Maurice something,” he said benevolently. “Once I gave that up, Maurice would fight Glenwood Brown. He got a title fight right away. He beat Glenwood Brown and he had the title back.” Though Hearns and Maurice Blocker were the same height, doubtful Blocker hits as hard as Hearns. At 15 rounds, Cuevas by late TKO, maybe suffering an early round flash knockdown himself. https://www.ringtv.com/514795-best-faced-simon-brown/
Cuevas underestimated as usual. I suggest Brown would have some slick moments but would end up punching air from his back like he did against Pettway. Cuevas was a killer. Bad night against Shields because he fought with a fever/flu. Still went 15 and still won.
Pipino by clean KO. He was a greater puncher at his peak. My opinion but I think he was too strong for even Simon in this type of fight.