One thing you're missing: Smaller size before compression does not necessarily imply smaller size after compression. For instance, /O2 has a tendency to generat

One thing you're missing: Smaller size before compression does not necessarily imply smaller size after compression. For instance, /O2 has a tendency to generate code that is difficult to compress. So it is always better to keep in mind how you achieve smaller file sizes after compression, and not worry so much about data sizes before compression.