Rudy Jaramillo is better known at the time as he is still active and employed as the Texas Rangers batting coach. Rudy like Lau never really made it as a player but found his niche as an instructor. Jaramillo parrots much of Lau's teaching but is more intense regarding instruction to the mental aspect of the at-bat. As it is difficult to say one is better than the other based on philosophy, a good way to gauge Jaramillo's success is to look at the success of the offenses he has developed.
The Rangers have never been a great team during his tenure, in fact the organization has been a bit of a revolving door for players. Non withstanding, Jaramillo continues to develop hitters that produce potent offensive attacks. From 90-93 when Rudy took his first MLB posting as a batting coach with the Astro's they regularly broke their club offensive records which landed him the Rangers job.
While in Texas his offense has been not just consistent or above average, but borders on stellar. From 1996 through the 2004 season the Rangers ranked in the top five in the League in team batting average, runs, slugging percentage, hits, and home runs. In the 1999 season Texas led all Major League teams in hits, slugging percentage, and team batting average ( A gaudy .293). In 2005 the Rangers hit 260 home runs which was the second-highest total in MLB history. His tenure in Texas, has produced 16 Silver Slugger Awards, four MVP Awards, three home run titles, two RBI championships and a batting title. The number increases if considering what players he developed achieved after leaving Texas. Not a shabby resume.
Jaramillo is further credited with developing the hitting of Juan Gonzalez, Atlanta's Mark Texeria, Michael Young, Ian Kinsler, Hank Blalock, and Detroits Ivan Rodriguez. Jaramillo is regularly discussed in talks concerning managerial positions and is currently the most sought after batting coach in the game at any level. His legend grows ever year.
While there have certainly been many fine batting coaches, there are none that come to mind or appear in research of bygone eras that have had the impact of Lau and Jaramillo. It is difficult to even say one is better than the other and is actually a debate I don't believe can ever be settled. Either way, these are probably the two best hitting instructors in the game ever.