I agreee that the iMac suffers from the same non-expandability as the Pro, and that the iMac video card is suboptimal. I too would far prefer an Nvidia GPU over the AMDs/ATIs that Apple prefers. My point is, these demerits aren’t new. Apple has been limiting even high end Macs to mid-performance hardware and sealing them in anti-expandable ways for quite some time. (Though I admit, the crippled design of the Mac Pro does mystify me.) Even the original Mac (with its 12" embedded torx screws and puny 60W power supply) hamstrung users from upgrading it. So this problem is not new.
My solution is the very one you suggest — I also own a generic PC box with more RAM and a fast Nvidia GPU (running Linux) that I use for heavy lifting. I think this course of action is inevitable. Apple’s top priority has long been to sell machines that look good. Competitve game play or GPGPU hacking remains too niche for the company beancounters to allow Jony Ive to go there.
Apple doesn’t make server hardware either (though they once did). That’s wise. I’m pretty sure every computer maker in that space now regrets going there. It’s the black hole of commodityland, which Apple rightly abhors.
Yes, the Apple ecosystem won’t float all boats. But personally, I’m OK with that. I don’t *want* to live entirely in one walled garden.