Bit late to the party but um... always grab the new genesis, especially after you bottom decked 1 of your 2 9 cost zoros, you want to cycle through your deck to get back to your win condition, also if they attach 1 don to RP law and swing with 4 don they are playing a 3 cost because almost nothing good in the deck costs 2 don and they dont want to waste an active don on a bottom deck so nami was safe the moment they attached only 1 don, 2 or 3 don would be a different story though.