Did you learn anything? I guess you're testing for consistency between the strap and the optical system.
There are definitely differences. In Georgia, at the Navigator Cup, I didn't have the HR strap, and it was clear the HR indication was drastically wrong. I submitted a report to Garmin. It seems to have improved. It seemed like it was picking up my walking cadence---running seemed okay.
You're supposed to tighten the watch before an event, if you're like me and leave the watch loose for day-to-day wear. I had it tight in Georgia.
I need to download the gpx files, open them in xml editors, and combine them in a spreadsheet so I can plot the two traces.