That's interesting because they both tend to be in people's minds and revered above similar pitchers, and they put it all together somewhat late in their careers.
Koufax had the better peak, but better enough to have a career better than Nolan's? I can't say.
Ryan started out so savage and chaotic. Fortunately for him he could overpower hitters and not give up many home runs, but that also spoke to the hitters in the early 70s. The ERA results were usually good, as we saw in 1972 at 2.28. BUT that was a year close to 1968 (he had 16 losses, fewer CGs than usual), and from year to year he could see ERA swings and WHIP as well. He got the most out of his high WHIPs but what about in numerous other decades? Would he be a rich-man's Daniel Cabrera instead of a true legend?
Once he learned to really pitch, or at least efficiently, he was 34 as was a very good older player after that. He was still wild and didn't have great ERA+ results, but I think he outpitched his stats.
But Koufax... ahh, heck, he was better, over about 7-8 years which is enough to tell... not the better career since Nolan had more than 400 starts of good quality.
JM: Only did that for a couple of years and then we had a conspiracy so it kind of turned me sour. Our league's commissioner, Lew Ford(notes) at the time, was doing some shady things that ... I'd rather not talk about [laughs].
DB: Isn't he in Japan right now?
JM: I don't know where Lou is right now. He's probably fleeing the authorities [laughs].