Hybrid picking isn’t compatible with every setup, grip or picking movement.
Everything is a compromise, and insisting on the facility to hybrid pick constrains the movement problem strongly, eliminating many possible solutions.
I’d argue DSX. The degree of supination required for a reverse dart-thrower based USX movement would result in the fingers not being immediately available for hybrid picking. With reverse dart-thower based DSX, the fingers can be available immediately.
It is possible to have immediately available hybrid picking with dart-thrower USX with hybrid picking, but this is a much less common movement pattern.
USX+hybrid has enormous capability, solving many of the “bad cases” of strict USX (notably what Chris Brooks calls “lone note exceptions”). However, the solutions of those “bad cases” are somehwat less obvious than those for DSX+hybrid.