For some reason I think of them as completely different names when they really aren't! This is going to sound silly but I didn't even make the connection that they were related until just now, haha. I muchhhh prefer
Hester, but that might just be because
Hester has not been as historically popular in the U.S. and therefore associated as a quintessential Old Lady Name. That normally wouldn't turn me off, but I can't really get on board with
Esther.
Basically,
Hester has an evenness about it that
Esther does not have IMO. It looks cleaner and has cooler literary associations. It's kind of fun but also kind of ugly. Fungly.