I also have a Mavic that I'm planning on selling (once a couple early adopter issues are resolved).
It's all about your use case. For mine, the Spark is a no brainer. My analogy is my DSLR, which I'll explain below.
I'm a videography and photography hobbyist. But I found I stopped carrying my DSLR because of weight and size issues. And we're not talking about a professional or prosumer full frame but a Canon Rebel (again which I chose because it was smaller/lighter). My iPhone became good enough because it was always with me. I enjoyed shooting videos and photos, but just as a part of my adventures. It's not THE reason for my adventures.
This has changed recently as I now have a lightweight mirrorless Sony a5100 DSLR. It's small enough that I can fit it in a pocket or in a corner of whatever bag I carry that day. I'm OK that the lenses are not as sharp as my Canon lenses because I wouldn't be carrying a DSLR otherwise.
Spark v. Mavic is similar. I love the Mavic and the video quality. But it's big enough and heavy enough that I have to consciously chose to bring it. Then, when I decide to use it, I have to find a spot to launch, unfold, remove the gimbal cover, remember to remove the gimbal lock, unfold the remote, then launch. The video I get is Prosumer quality but, the best video is the video you take.
I'll carry and use the Spark way more often than I've used my Mavic.
Here's the features I care about:
Usable without controller: One less thing to carry, which will allow me to use it for trips where weight/space is an issue. Like camping or Backpacking.
Micro USB charging: See above. I'll already have a 6 Port USB charging hub for travel and can just plug the Spark into that. Plus for backpacking/camping I'll have a small solar panel
Lightweight: The Spark alone is 70% lighter (1.7lbs!) than Mavic+Controller. Spark+Contoller is about 1.1 lbs lighter (more than 45% lighter) than the Mavic equivalent. My wife won't notice me throwing the 300g Spark into the family daypack for hiking, travel, etc. Also, the Mavic+Controller is way too heavy for Backpacking, for example. Spark is under 11 oz and AC+RC is just over 20oz.
Quick Setup: The Spark is ready to go with a quick power on and palm launch. No unfolding, which would make it heavier and take more time to launch. No worrying about taking off on a dirt trail or tall grass.
I'm not 100% happy with it, but I'm hoping those issues can be solved with future firmware updates.
Real world weights:
Mavic AC: 756g
Mavic RC: 311g
Spark AC: 302g
Spark RC: 273g.
Very nice!
As a professional photographer and videographer I have experienced the same thing you described. For non-paid gigs like vacations the only shots that matter are the ones that get taken, and that's usually with your phone or something small. Though I find my Mavic fits nicely in a small sling pack and was quick enough to set up that we could easily do a large group selfie on our last vacation without people getting antsy. 20 minutes per battery and virtually unlimited range also made it possible to shoot more things on our vacation than just us.
Your other points are very well taken. Especially - I didn't realize that the Spark could be USB recharged. That's potentially huge. I'm eager to test all that means with a large Anker battery. If anyone else knows, please share.
Usable without a controller and Quick Setup still remain to be proven. Posts like this one: WTF DJI?... WTF!!?!?!@!?!!!! First Spark flyaway would have to completely go away. And with them, the conventional wisdom that responsible flying requires that you also have a backup controller ready. If those issues do go away, I agree, that would be better than the Mavic. But $500 better? That's the price of an iPhone for just one function.
Still, I'm so enamored with the idea of flying in public areas that this is almost enough to convince me.
Thanks for being so thorough!