I would suggest to use identical cups. Surface area makes a difference. Thanks for your work though, I got the Duo. I also believe it's a superior build. Also, when we talk about choice, let's take price out of the picture first. Also brew method I feel makes a difference too. Chemex VS v60 could alter preference between the two.

I got the Columbian and Congo from Good Brothers and going to have that this weekend sometime, along with the Lychee from Hydrangea.

If interested, try the Guatemala Red Caturra Orange Honey process from Bean & Bean. It was a COE coffee and fantastic. One of the best that I ordered.

Saw the video of your friend comparing espresso with the Duo to DF83 and he preferred the 83, but it was close. Do you agree?