If you are just using code to define a range, then it would be best to use the offset formula. Then you wouldn't have to save it as a macro enabled workbook as well.
If you are using other code, then why not use the defined range code.
The code is very efficient, it just finds the last used cell in a column, it will not slow down the program.

More on defined ranges.
http://support.microsoft.com/kb/830287