Gadget for Mac vs Korg Legacy Collection

[paogoz]

Hello! First post here.
I am trying to figure out what would be the main differences in sound quality between Mono/Poly, Arp, and other possible Gadget for Mac counterparts (I own iMS20, iPolysix and all other Gadgets).
One thing I don't get is why should one buy a Legacy Collection Mono/Poly if he already owns the Gadget counterpart?
I know there are many limitations in Gadgets, but I am tempted by having all modules in vst format. In the other hand, I guess Legacy Collection should be more in depth control and quality. I have to take a decision before Christmas sales end.