All rounder mate and I've had both systems
I can update a little having used this 12v sander on a smallsih woodworking job and it worked really nicely, so easy to handle with one hand, though I think would be better using a proper dust extraction device (I was just using the supplied bag, which obviously doesn't provide any suction). You might not want to use it for any large construction jobs but like all these tools it certainly works well in the right context.
Out of interest, what is your trade as it sounds like it's informing your opinion? I'm sure your comments are all totally valid (no question they aren't as powerful etc as the 18v systems) but factors such as form factor (compact size, super ergonomic, low weight etc) CAN be important to some people / trades. My bro in law is a cabinet maker/fitter, swears by these. High power devices aren't required, he uses the 12v jigsaw, planer, impact and drill for most things wood related. But does have the 18v drill for masonry and corded orbital for the reason you've mentioned. Take your point on this sander though, looks like there's no point in replacing my corded one.
I didn't say the best , value for money is far better...
They're obviously not as potent as the 18V range, nobody is disuputing that, and almost certainly unsuited to a lot of heavier construction jobs, but their weight and size have lots of advantages and IMO they do work....people swear by the jigsaw, drills/drivers, I've used the grinder for cutting floor tiles with much more precision than I could manage with my larger grinder. The biggest, most powerful option isn't always the best.