Wolfox

First off, it's Jeigan. Secondly, that's kind of a poorly worded question. There are some Ests that are amazing such as Delthea and SoV Est which due to how the level up systems work make them stand out. There are also some fantastic and even game breaking Jeigans as well which most of those are Oifeys.

I guess I'll have to be on the Jeigan side purely due to them always having a use and serving the role as the early game savior. They also are strong even in the mid-game when you need an additional unit to help guard or rush in to stop a bandit from destroying a house.

I don't think there has ever been a useless Jayginn (yes, I know), while almost all Ests are obsolete when playing at least semi-efficiently (generally how I play). The only good Est off the top of my head is FE5's Sara, who's got 80% offensive growths,

Ests are usually more charming but they're just too much work much of the time. Plus Jaegens can be really useful on harder difficulties, like Marcus in Blazing sword.