well purely from a build qualoity point of view - the sapphire plus.
It has a more rigid frame and actual linear rails.
To convert it to a direct drive extruder is a simple job that involves a small printed bracket (it's the same extruder/hotend setup as my sapphire pro2)

The tronxy has a slightky larger build volume, uses metal guide wheels and not linear rails.
It should be fairly easy to convert to direct drive - but you'd have to ask autowiz - although be prepared to be told it needs a total rebuild :-)

But as the speed of a corexy - and any other 3d printer for that matter. Is largely down to the solidity and rigidity of the frame and how straight and true the extruder carriage runs , I would personally go for the sapphire plus.