string.sub vs string.byte

[Adrian Sietsma <adrian_groups@...>]

I am writing an app that must test every character in an input stream.
As i understand it, "s1 = string.sub(s,n,n)" must construct a new string 
each time it is called.
Would "b = string.byte(s,n)" be appreciably faster ?
(although all my comparisons would then be number, rather than string, 
and i believe slower)

Adrian