Sony certainly does have a significant advantage as the only mirrorless system with APS-C and FF options with the same accessories and decent lens compatibility. I don't personally like their interface, but it is pretty consistent across models as well, with modifications for cameras with fewer controls
FF lenses are often, although not always, bulky and odd focal lengths on APS-C (although long telephotos work very well on APS-C - they get "longer", and they're always bulky, regardless of format).. This is certainly not a unique Sony problem. Canon and Nikon DSLRs have the same issue of largely poor-quality APS-C lenses supplemented by excellent FF lenses that may not be what you want on the smaller format.
Where Sony has a huge advantage is in accessories other than lenses - flash systems and the like are completely compatible. I use Nikon Z and Fuji, and even my memory cards don't cross over!
Everybody has battery issues - neither option is completely satisfactory. Some manufacturers stick to one very small battery that fits in their smallest camera and end up like Fuji. The NP-W126 is completely ridiculous in some of the larger cameras, especially the X-H1.
Others use a larger battery in larger cameras and wind up without the problem of a power-hungry camera with a tiny battery, but with two or more incompatible batteries in many photographers' bags, as Sony has done with the larger battery in recent FF models.
Nikon has done as good a job of this as anyone - the ubiquitous EN-EL15 series is large enough to power a pro camera, and shows up in the more serious APS-C DSLRs, all the FF DSLRs except the D3-D5 series, and the Z6/Z7. If they come out with an APS-C Z-series body, I hope they squeeze the EN-EL15b in...
Overall, this doesn't change much that I can see - a decent backup body for Sony FF shooters that gives a different set of focal lengths. It's clearly superior to the A6300, unless you get the 6300 on clearance for much less.
It's not that much more camera than the A6000 for half the price, although the faster AF is useful. If you have Sony FF and don't care about the different focal lengths, the price difference to the A7II is relatively small for FF, IBIS and other features? The A7II is presently $1398, a meaningful difference - but it has been as low as $998, and it probably will be again.
If you don't have Sony FF, Sony APS-C isn't compelling on its own because of the poor lens selection. if you're going to use FF lenses but haven't considered an FF body, why not an A7II? The A6400 is $1298 with a decent lens (18-135). The A7II is $1598 with the 28-70. You get a much wider zoom range with the A6400, but you get into the FF system Sony's really supporting with the A7II