Not everyone leaves dynamics for 'stats. I grew up on 'stats; the SR-001 and SR-404 were my first good headphones, and I've left them for dynamics, though I am coming back to 'stats now with the EH-1.2B. Honestly, it's a matter of preference and perspective, and each system has its strengths and weaknesses. I'd say that 'stats have more high-end potential, but in the low end dynamics give you more bang for the buck.
A dynamic's main strength is excursion; the driver moves a lot of air, and that gives it a lot of tactile impact. On a good dynamic, you feel that you can literally reach out and touch the instruments. Basslines have heft and flow, and you can feel the drivers moving the air, which in turn you can feel pounding your eardrums. Some say that the thump is a coloration and truly transparent planar speakers are more accurate because they don't have it, but stand next to a drum kit, sit in the front row of an organ concert, or just simply play a grand piano, and you'll quickly realize how important heft and impact is to the realism and emotional involvement of the music.
The main problem dynamic drivers have is impulse response. There is a big, heavy voice coil hanging off the membrane, and no matter how well you drive it or how much motive force you throw at it, it will never be as quick as a nearly weightless electrostatic membrane. That means that as music becomes more dense and more complex, dynamics start losing their resolution, and everything becomes a homogenous mass of sound. On an electrostat, everything is clearly defined always, no matter how dense and hectic things get. Dynamics also tend to lose resolution as you go down the frequency range; while 'stats are detailed throughout, and even if dynamics can keep up with 'stats in treble detail (I dare you to listen to the K1k or a Qualia 010 off a good system and think otherwise) they can't keep up in bass detail.
On a 'stat, though, music seems to come out of thin air. With a dynamic, you're always inherently aware that there is a system playing back the music; with a 'stat, the system often disappears and you're left with nothing but the music. This is eerie and disconcerting at first if you are expecting to listen to a good system since you won't hear the system (or rather, it will me more difficult to hear the system) but once you adjust to it, it simply becomes a different presentation. The lack of the tactile element makes the music seem more ethereal, not necessarily thinner, but definitely less palpable, and you're inherently aware that there's something missing. At the same time, you can hear further into the recording, and a good 'stat's resolving power illuminates every dark nook and cranny of what's on the album. And as the music becomes denser, faster, and more intense, 'stats just get their groove on, while dynamics start to struggle and fall behind.
For me, neither is perfect. I've attempted to build a dynamic system with the speed of an electrostat, and it's coming along quite nicely. It's not there yet, but I'm already getting results I can live with - and there's much, much further I can go. At the same time, I'm also putting together an electrostatic system that will have some real tactile impact. At the end of the day, I'll compare the two, and decide what to do from there. I may very well end up keeping both.
Electrostats never had any magic for me, but I guess that's because I grew up with them. They certainly have spoiled me to the core, but that's the price of keeping your ears happy. Which, strangely enough, has never been the case for me until lately.
