Seales was a full-blown middleweight and a southpaw. He gave some people fits but was a shade below world class. If we assume this takes place when it most likely could have, say mid-1979 when Leonard stepped up to middle to fight Marcos Geraldo, I think Leonard takes a decision. Seales had recently been taken out in one by Hagler and lost a decision to Ayub Kalule and was more or less past beating contenders (although he was giving good middleweights good fights). The further past this time frame, the more likely Leonard takes him out. Seales goes into decline and Leonard is on the rise, growing more into his body, and while it was a good fight he more or less manhandled Kalule. If we’re talking some kind of fantasy fight where it’s each at his best, Leonard is still the winner. There’s not really IMO a version of Seales that is better than the best version of Leonard.
Good fight, I'd take Seales TBH. Sugar Leonard at MW was not an overwhelming force. I think Leonard has a hard time with his length and skillset. A prime Hagler had some moderate struggles with Seales tbh although ultimately showed that he was the superior fighter. Seales was tall, long, a mover and a southpaw and Leonard really didn't do anything of note at all at MW (his only good "win" I thought he lost to Hagler), I say in a 3 fight series Seales wins 2-1
There's no version of Ray Seales that beat prime Ray Leonard. The bigger, stronger version that beat the hell out of Kalule would grind him down and stop him. It's the Larry Bonds fight for Leonard again. Seales was a slick south paw.