We do millions of simulations to collect data points for all relevant builds (talent, legendary, covenant, soulbind, conduit, stats). We then do an analysis of that data and build a mathematical model from it. The suggestions you see on our site are what that model predicts to be the best choice for your current situation.
Nobody does an analysis as comprehensive as ours. Those other sources of information are doing a small subset of the analysis that we do. It is common for our suggestions to be slightly different.
You are not going to see a big difference in-game between those two soulbinds, so it’s hard to really say for sure which is better “for sure”. I have found that our model of the game is very good and I follow it. I think two potency conduit builds will be better than taking marrowed with bonesmith in the long run, so Emeni will ultimately be BiS.