optimal build?

Watching pros like Flame playing renekton, they seem to always build tiamat-BC-TH-GS as a core. Is this the best build or is BC-TH-SV-DMP-GS just as good? Tiamat first isn't as needed outside of pro play because wave management isn't as important, I think.

I'm not confident enough at renkton to build him AD with lethality or BotRK, so I'm only looking for tank builds.