Where did you get this info from? I'm pretty sure the writers never said Synthesis was the best choice. There is no best choice for every player. We all have our own best ending.
The Catalyst presents it as the ideal choice. It also requires a higher EMS score to unlock than Control or Destroy, and with the Extended Cut it is given an epilogue that make the results sound like it created some sort of utopia. All that was missing was a flashing neon sign above the decision chamber telling Shepard to Go Green. The favoritism among the lead writers for Synthesis was fairly heavy-handed.
Refuse is an actual choice, not a Critical Mission Failure. Tho I agree that this ending should not be recognized, just as Shepard's death in ME2 wasn't recognized.
Refuse is a choice, but it is also a very bad one that ends with everyone Shepard knows dead and the extinction of every space faring species in the galaxy including humanity. It results in a decisive defeat for the Council races in The Reaper War and the most disastrous outcome for a war in all of human history. It is a critical mission failure.
Again, where are you getting this info from? When have the writers ever said they didn't like Control? How do you know Control is not liked by the fans? You have no idea how many people actually like this ending. If what you're saying is based from what you've see on BSN, you're absolutely wrong.
I didn't say that the writers didn't like Control. I said they presented Synthesis as the best choice.
As for the fans, every poll done on ending choices has shown Destroy to be far and away the fan favorite. The results were not even close, and some of those had very large sample sizes. On that note I didn't say that the fans disliked Control either. I just said that it wasn't the most popular ending among the fans.