Commands such as grep this /that/file will always run faster than commands such as cat /that/file | grep this.
Timing differences measured in seconds don't count for much for scripts that run against small data collections. Quick and dirty scripts can still be quick and dirty. But scripts that are intended to run against big data problems can benefit significantly from more careful scripting techniques.
Read more of Sandra Henry-Stocker's Unix as a Second Language blog and follow the latest IT news at ITworld, Twitter and Facebook.