Ghosting works in Solaris. You just need everything to be part of the same stage:
The main sell of USD is not its interoperability. Alembic already does that very well in production. USD offers much more than interoperability, in the way of non-destructive scene management and inter-departmental scene and asset layering, apart from other nice features built into its core. It is a godsend in production, and no other system even attempts to do what it does. It is not a technology aimed at individuals, so I guess if you have to ask, you very likely don't need it (I certainly don't).
This is not true at all. You can definitely animate positions on any light, and here is an example of lights in Solaris instanced onto points:
Leaving aside the Solaris-exclusive interactive highlight and shadow placement (that SideFX could easily bring to /obj if they wanted), Solaris offers a trivial way to non-destructively set up and lights, and reuse them across shots. You compare it to takes, and there is some overlap in this use case, but you would need to generate a fair few takes to achieve what Solaris can do with a little branching.
The other, less mentioned, advantage is the visual layout of your scene structure, something that takes does not offer at all. Knowing what lights affect what shot - at a glance - is a massive productivity boost.
I'd say to each their own, though. If takes works better for you, you should use takes. I vastly prefer setting up lights in Solaris, and that will be my preferred method going forward. It's good to have choice.