I know FlexTrans is superior to SegWit, because it actually fixes a lot of problems SegWit doesn't fix.
Just because the idiot Zander says that it is superior, that doesn't make so. FlexTrans was riddled with all kinds of bugs since day one (not the kind of 'development in progress' bugs, but the kind of 'I know primary school CS' ones). Additionally it requires an unnecessary HF. So why is SegWit being pushed through like it's the only solution, when it's clearly inferior.
It is up to you to prove that it is inferior in the first place. 
It is already explained here:
How do SegWit and FlexTrans compare?