Kim Il-kwon evaluates that Choi Dong-won was better than Sun Dong-yol.

‌He evaluates that Choi Dong-won was the better pitcher when comparing their actual pitching forms and physical stamina observed from the sidelines at the time.
He says that no one can match Choi Dong-won in terms of control,
and while Sun Dong-yol had a slight edge in terms of velocity,
there was a nuance that there were differences in their ages and eras. Although he didn't mention this directly, it seems he perceives that Choi Dong-won was at a disadvantage regarding velocity compared to his actual ability (this is just my assumption, so please take it with a grain of salt).
Also, looking at their ability to pitch consecutive games, he says that even if they pitch up to 15 innings, Sun Dong-yol would be exhausted the next day, whereas Choi Dong-won would be out on the field training again, meaning he was physically superior.
In any case, he overall states that Choi Dong-won was the better pitcher.
As for Lim Ho-gyun, he expressed the sentiment that it is difficult to distinguish superiority between Choi Dong-won and Sun Dong-yol, as they are more or less on par...