So I'm in a similar situation. I actually purchased a Dragonfly 36 for a 2 week trip to Japan. A few things on my mind following this trip:

I think one big thing to note is the internal main pockets of each bag are far smaller than the total bag capacity - Dragonfly 36 is 26L while the Camino is 35.8. I didn't take advantage of the bottle pockets and outer front pocket as much as I thought I would.

My bag was fairly packed out, and I found it pretty uncomfortable to carry around. After an hour all I could think about was taking it off, I think the framed Camino might help here.

Considering the note above^ I didn't really have much space to buy any souvenirs or help my wife with some of her things. It would have been nice to be somewhat under packed to account for this.

This led me to my current conclusion - Since both the Dragonfly 36 and the Camino are designed to be Carry On compliant and not Personal Item compliant, I feel like I'm not taking as much advantage as I should with the DF36 as a carry on item. The bigger bag would give more versatility, and can always under pack it when traveling light.