These are undoubtedly two idols who established a legacy away from their groups. Recognized as solo artists without needing a group attached to them. I would break it down to 3 parts GP/fan support, Solo work, Awards. 1.GP/Fan support- Both are known but i would give this to GD he's the biggest idol in Korea. Guarantee everyone knows or at least heard his name. 2.Solo work- For me i like Zico's work better. Zico on The Block, Gallery, Television are better as whole then G Dragon's discography. Zico is a better producer to me also. 3.Awards- Both have won awards for their work. GD might have more. But i will say besides the typical idol award shows Zico won at the Korean hip hop Awards multiple times. Accepted as idol and rapper. I give it a tie. For me i prefer Zico.