It's gotta be Rod. Otherwise, all the GOAT formulations have to be scrapped and the whole discussion started from scratch. You see, Mac isn't even in the first tier of GOAT candidates, while Rocket is in the top 3 for everyone but Jack Kramer. So if Mac beats Rod all these lists have to be redrawn, which would require hundreds more horribly boring and pedantic threads wherein middle-aged armchair historians fight with each other like teenage girls. If Mac is better than Rod than he's better than Rosewall, and maybe even the supernaturally talented Lew Hoad!!! (And if Mac is as good as Hoad then it would come down to who had the better back, in which case Mac is the GOAT!)
No, no, no. Laver beats McEnroe 9 times out of 10 regardless of surface. I've watched 5 hours and 36 minutes of Laver highlights on Youtube, so you can trust me on this.