Except that if you were using a text file, you use different flags or turn it on or off on a per executable file basis checked on process start and would not have to re-parse the symlink every time you malloc something.
Then why parsing a human-readable file that could, conceivably, activate a much richer debugging option-set is such a huge overhead as to make the symlink way a better option? Is the setting system-wide or process-wide?
Sorry, but I just can't see why it would be a better option.