I think Rafa and Noles 1st serves are pretty similar in quality. Nole might be more aggressive with his but Nadal has some nasty lefty spin. I think Nole hits bigger second serves though. From the back of the court they are similar but nole is willing to hit flatter and be much more aggressive. Rafa has always hesitated to be aggressive when given the chance where Nole is more than comfortable going after it. Rafa always tries to out steady Nole and spends way to much energy running corner to corner just trying to be a backboard.
Please excuse my punctuation and grammar.