The big advantage of the DA with the embedded memory is that its largely all contained.. Add a clock, power, I/O, ethernet or usb if you need, and your done. The Arm based processors need DRAM attached on the side and that does complicate things and size..
I use a PIC32MZ EF part in a couple of products. I am personally excited for the DA.
The reason? Exactly what you said... I get up to 2MB flash, 32MB of RAM, and a fast SD Card controller in a TQFP package. Although, I might have to reconsider the BGA package since the pitch on the BGA isn't all that bad - inspection/rework sucks though.
On the hardware side, the engineering is much easier.... I don't have to deal with DDR routing. I have an onboard ethernet MAC, USB phy, etc. I've looked at lots of processors over the years and I just haven't been able to find any other processor which is both the combination of easy to design with, easy to assemble, and has the features I need.
In short, the hardware engineering for a PIC32 isn't much worse than any other PIC that I've ever dealt with. In the PIC32MZ family I get 200MPS, hardware crypto and floating point, lots of memory, low power consumption, etc. For my application this is perfect. The DA parts gain me so much more for not a lot more money than I'm paying for the EF parts. I have a product coming up soon that for the advanced versions of the product, I was worried about fitting the entire design in the EF, so this might fit just fine. I AM going to wait a bit before committing after having been bit with the EC issue.
People like to whine about Harmony. They also like to whine about MPLAB X and the XC compilers, and well, everything else. For me, I don't see what the big problem is. There's been a few bugs, but no show stoppers in recent harmony versions. If you're trying to use harmony to build some 'next to the hardware' application or something which requires medical grade reliability, then harmony isn't for you. If instead, you're looking for a decent TCP/IP and USB stack engineered for a resource constrained system, it really isn't that bad. Use harmony for what it's good at and write your own code for what it isn't.
I totally get why Linux is attractive though. I just don't feel that this part was designed for that application in mind.