Today I'll compare arguably the two best left-handed pitchers of all-time in Major League history, and two of the best pitchers in general. First, I'll list their career stats, in comparison, before I delve into specifics.
Carlton- 329-244 (.574%), 3.22 ERA, 4136 Ks, 5217.2 IP, 1833 BBs, 709 GS, 1.247 WHIP, 8.1 H/9, 0.7 HR/9, 3.2 BB/9, 7.1 K/9, 2.26 SO/BB
Johnson- 303- 166 (.646%), 3.29 ERA, 4875 Ks, 4135.1 IP, 1497 BBs, 603 GS, 1.171 WHIP, 7.3 H/9, 0.9 HR/9, 3.3 BB/9, 10.6 K/9, 3.26 SO/BB
Excluding wins, losses, and winning percentage; because I feel wins don't represent how good/bad a pitcher was, because baseball's a team sport; based on the stats above, they're even at six apiece. If you take away/exclude totals, and base the comparison on averages, Johnson wins slightly 4-3 (WHIP, H/9, K/9, and SO/BB ratio).
Carlton pitched for 24 years; 15 of which were with Philadelphia, while Johnson pitched for 22. Since Johnson was traded mid-season twice, he played both 12 seasons in the AL and NL in his career, while Carlton pitched primarily in the National League with Philly and St. Louis.
Johnson is arguably the best strikeout pitcher ever, in any decade, for either LHP/RHP. Per 162 games, in his career the "Big Unit" averaged a whopping 10.6 strikeouts per nine innings. That's a baseball record that stands until this day. His closest competitors in that category are former-Cubs' starter Kerry Wood and Pedro Martinez. Wood pitched eight fewer seasons, while Martinez -- like Johnson -- is regarded as one of the all-time greats. The latter pitched in 18 seasons.
You can make a case for either pitcher. Johnson for over a decade primarily faced more position players because of the designated hitter in the American League, thus meaning he faced tough competition with some of the league's best sluggers in the AL facing him at DH. Having to face another batter, instead of a pitcher, is tough in itself.
Steve won his four Cy Young Awards in 1972, 1977, 1980, and 1982. Carlton won two World Series' titles; in 1967 with the "El Birdos" St. Louis Cardinals (who had four future Hall-of-Famers on their team; Carlton, Lou Brock, Bob Gibson, and Orlando Cepeda) and with Philadelphia, the same year Carlton won the CYA, in 1980. On the flip side, the Big Unit won one more Cy Young Award than Carlton did, in five (1995, 1999-2002), but one fewer title. His lone World Series title came with the 2001 Diamondbacks. Curt Schilling, Johnson's World Series champion teammate that year, shared the World Series MVP trophy with Johnson after the series with New York concluded.
Carlton's # 32 jersey went on to be retired by the Phillies years later, while the Seattle Mariners honored Johnson by inducting him into the team's Hall of Fame. The former pitched for six different teams in his career: St. Louis (1965-71), Philadelphia (1972-86), San Francisco (1986), the Chicago White Sox (1986), Cleveland (1987), and Minnesota (1987-88). The latter pitched for six teams as well throughout his 22-year career: Montreal (1988-89), Seattle (1989-1998), Houston (1998), Arizona (1999-2004, 2007-08), the Yankees (2005-06), and San Francisco (2009).
Lefty, despite his legacy, never threw a no-hitter; but threw six one-hitters in his career. Johnson, however, not only threw two no-hitters but a perfect game as well. Johnson's first no-hitter came in June of 1990 with Seattle and his second no-hitter -- and lone perfect game -- came in May of 2004 with the Diamondbacks. Randy's perfect game that year was just the 17th in baseball history. Additionally, in accomplishing his second-career no-hitter, Johnson became only the fifth pitcher in history to throw at least one no-hitter in both leagues (Cy Young, Jim Bunning, Nolan Ryan, and Hideo Nomo all did it prior).
Most legendary pitchers, and even good pitchers, have a larger span of time in which they were regarded as in their prime; considering their superiority to lesser known and talented pitchers of their time. Both lefty and Randy were simply fantastic in their prime, but let's take a look at where the two ended up towards the latter part of their career, to gain perspective in the match-up.
Since both pitched well into their 40s, I'll compare their statistics from age 40 onward.
Carlton- (age 40-43)- 16-37 (.301 winning percentage), 5.21 ERA, 5.23 strikeouts/9, 82.5 IP/year, 1.83 WHIP,
Johnson- (age 40-45)- 73-52 (.584 winning percentage), 3.87 ERA, 9.1 strikeouts/9, 192 IP/year, 1.20 WHIP
Carlton declined tremendously, as shown in the statistics laid out above, towards the end of his career; although he didn't pitch much per year- especially compared to earlier on in his career when he was a well-known workhouse. His ERA flat lined, his strikeouts dipped a bit, but all in all his ERA and innings pitched/year were the notable differences in his game, or lack thereof. This plays a fair part in determining who's better all-time.
Johnson, however, still pitched well; albeit not as dominant, but that's not saying much considering what he did in his prime; in his later years, as shown above. He averaged over 100 more innings/year than Carlton did, all while pitching one more year than the latter did (even though Johnson started his career later than Carlton did). The former's 3.87 ERA from his 40s and upward was decent but not great; but his strikeout-rate, consistency considering his age, and his superiority to Carlton from 40 onward give Johnson the edge here by a good margin.
Carlton- 10-time All-Star, 4-time Cy Young Award winner, 5-time Top-10 MVP Voting, 5-time strikeout/innings-pitched champ, 1-time ERA champ/Gold-Glove winner, 1994 1st-Ballot Hall-of-Famer
Johnson- 10-time All-Star, 5-time Cy Young Award winner, 9-time MLB strikeout champ, 2-time Top-10 MVP Voting/innings-pitched champ, 4-time MLB ERA Leader/Champion
Simply put: Carlton was a workhorse, while Johnson was a strikeout machine. On the downside for the latter, Johnson for years struggled with control. From 1990-92, he averaged 139 walks/year; including 152 in 1991 with Seattle. But, from a silver lining standpoint -- in Johnson's favor --, the Big Unit's walk totals went down dramatically over his career, as he improved his control, lowered his walk total, and yet continued his dominance from a strikeout standpoint.
His walk totals/year were still significantly high, Johnson's, but Carlton wasn't any better from a control standpoint. In the four consecutive seasons that Johnson won the Cy Young Award and compiled 300 or more strikeouts from 1999-2002, he averaged 72 walks/season.
Despite Johnson's early-career control problems, he actually averages fewer walks in his career, per 162 games, than Carlton does; 83 to 86. Carlton was also inconsistent throughout his career too, maybe most likely due to his workload affecting his consistency- or lack thereof.
After lefty's insane 27-10, Cy Young Award-winning 1972 season, the following year he went just 13-20 with a 3.90 ERA. He led the league in losses and his ERA, compared to the year before, went down almost two runs from 1.97 to 3.90. Although his win-loss record and ERA were poor, he still showed his work ethic by leading the league in innings pitched (293.1) and batters faced (1262).
Six times Randy had 300 or more strikeouts in a year, including his career-best 372 in 2001 with Arizona. Carlton, in comparison, only had 300+ strikeouts in a single-season once; in his miraculous 27-10 1972 season.
Carlton should have, in my mind, won the '72 NL MVP award over Cincinnati's Johnny Bench, but Johnson had equally MVP-caliber seasons, and was more consistent throughout his career. And both pitched 20+ seasons as well, so it wasn't as if Johnson or Carlton had more leverage in that category of games pitched/years played- even though Carlton pitched slightly longer.
From an unbiased, truly-honest point-of-view, I have to go with Randy Johnson over Carlton, unfortunately. Both were special, dominant, legendary pitchers, but Johnson was arguably the greatest strikeout pitcher ever, was consistent, pitched great vs. tough lineups and in both leagues, and was simply superior in many categories/aspects to Carlton, despite the latter's accomplishments and legendary status.
Sure, Carlton was rightfully inducted into the Hall-of-Fame in 1994, but Johnson will get his turn next year when he makes his first trip onto the Hall-of-Fame ballot. Since there's a five-year waiting period from when a player last played/pitched until he's eligible to be on the ballot, and since Johnson last pitched in 2009, the waiting period hasn't commenced yet.
But when it does, expect Johnson to not only be a first-ballot Hall-of-Famer, and rightfully so, but to be receiving plenty of votes at that; and not just the required minimum 75% of the votes. Either way, if you were to ask most Major League batters from the decades that each pitcher pitched in, they would tell you straight-forward that they didn't enjoy, and never did, facing that respective pitcher.