Author here - I'm advocating the latter.

I agree with you to a point. However, I believe that those things that have been with us for decades: sound cards, 2D graphics adaptors, network cards, etc. can be done in FPGAs, and should be.

The speed is there, and the power used by the southbridge and peripherals is eclipsed by the processor and the screen backlight, so I don't think the power consumption is worth worrying about (I'd be interested to see evidence to the contrary, though).

Put another way: much of the foundational chips on motherboard are no long performance-sensitive, so we shouldn't be paying a compatibility price for it.