Hi Erik,
I like this post, because it allows me to investigate many points that are often undertimated when buying a radio.
The "natively" use of APIs is a implicit assumption when you consider the last SDR rigs, from Flex to MB1 going through 7610, Anan and K4, are first of all network rigs regardless they are used remotely or not.
A network connection can (ideally) transfer 1Gbit of data per second so it is odd forcing the whole system to be used trough a serial ports that have 115200 byte per second speed (when you are lucky) and virtual cables that overdrive your cpu just to convert a stream of data.
Many of the software you mentioned can be used with EESDR as well or they just overcome some missing SmartSDR features.
I can agree with your point of view and your list of disappointments, but consider that Flexradio is there from 15 years or more, while Expert is relatively younger.
And this is not brand loyalty, it is a different way of watching the same things from different perspectives.
73' Enzo, iw7dmh