I have been fortunate to have three of the older versions. I owned some of the 1980's vintage Stax Lamda Pro earspeakers. I had the adapter and drove them with whatever power amp was on hand. They were nice, open, detailed and fast sounding yet I didn't consider them more revealing than my electrostatic loudspeakers. Simply didn't use them enough so sold them. Had some of the SR80 electrets from Stax. Similar sound for less money and bulk. Still power amplifier driven.
I also happened upon some of the original Koss ESP9 electrostats. Driven by an amplifier too. These had a smooth warm sound which I preferred for most music actually. Still I didn't keep them as you are stuck in your listening room connected to a power amp so why not listen to speakers.
So for real portable on the move use I settled on some Nakamichi SP7's for about a decade. Then had a fling with Grado SR60, SR80 and briefly SR225s. They seemed good yet always ended up being fatiguing to me. Too hot in the upper mids and hard sounding. Then some Beyer DT880's which I still like. Most recently some Sony 7510s.
So none of this tells you much about current planars. I think I would view them much like the old Stax. While they might not need 150 watts to drive them, they almost surely need some headphone amp that isn't exactly truly portable. So again if I have to carry around an amp it will end up used mostly at home, and I have speakers I enjoy more.