Here is my reasoning for why I tend to bring both:
The first reason is the load size. I like the load size on the PAX more. It gets me to where I need to be and it does it in the same amount of time the DaVinci would take.
The second reason is the vapor heat. I can be a wimp when it comes to dry/hot vapor. The PAX is like a joint in that it is hot and dry, I was not a big joint smoker they irritate my throat... any dry vaporizer irritates my throat. The DaVinci irritates it a little less then the PAX.
I don't mind the throat irritation from the PAX when I am trying to medicate to my preferred level. One bowl from the PAX is less irritating then three from the DaVinci. When I am medicated enough though, and I just wan to boost or maintain. I find the DaVinci works with one session, and is a little less harsh on the throat. So for the maintenance or boosting sessions I reach for the DaVinci.
If I use the DaVinci and I only do one bowl at a time I can last about 45 mintues before I want to do another bowl. If I am using the PAX I can last about an hour and a half sometimes two hours. Here is a good example of my usage preference.
I am on my way to the ballet: On the way there I will start using the PAX about 15 mintues before we arrive at the parking garage. I am done by the time we are parked. Usually the ballet has 2 sometimes 3 intermissions. I will medicate during each intermission... it is the only way I can sit in those chairs, they kill my bad back. I know that it will be about 45 minutes to an hour before the next intermission. During intermission, I will go out and use the DaVinci. On the way home if I need to medicate again, I would probably use the PAX... otherwise I would wait to get home and use something at home.