I think both look good but i'd be doing the slats yellow IMO, just so it looks standard from the factory. You don't need to dress it up so it looks different to other golfs, cus you've already got a rare special edition golf thats different to other golfs anyway.
But like anything, its your golf, do what you think looks best, everyone will have different opinions on here. Do the bottom bit first and spray the slats yellow later if you fancy a change, or you can always buy another grille and do both!!!