Sasuke's ameno is FTG with no need of markings. So its like an improved version of it.
Ameno > FTG
edit: none of them is faster. their speed is the same, they're both instant
They're both instant. But execution and usage, Ameno is superior. You teleport to where you look, thats it.
That is it's key flaw because Ameno is limited in the range it's effective and once outside this it is effectively useless and that is where FTG is superior.
Only in that regard. In all other, it is inferior.
It needs a marking. So user can't teleport anywhere he likes, he needs to prepare a marking to where he'll teleport. In a battle, Ameno is vastly superior.