I see little advantage over the quick hitch system, but several disadvantages. May just be me.
Disadvantage #1 would be the requirment to have a delta receiver on each implement. True, the implements may need to be altered to comply with the quick hitch's, but no more than needed to refit a delta receiver (IMO).
#2 would be, for me, fewer alternate uses that the quick hitch can be put to....such as the top hook for a set of logging tongs, welded grab hooks for hooking chains to and pulling things. The delta hook just seems to have the one application.
#3 would be visibility of the attachment. I can look through the arch in the quick hitch (iMatch for me) and see the tiller, the blade, the box scraper, etc. Not so much with the plates of the delta hook.
Granted, looks like when the delta hook is hooked and going, it will do the job of holding the attachment.