I tried 2 different servos in my car yesterday.
Question; one of the servos needs ~110% left epa and ~120% right epa to get maximum turning.
The other one needs only ~80% both left and right.
What does this tell you about the servos?
(One of them is a cheap one, the other one a known brand).

That the two servos process the signal from the receiver differently.

If you've got full steering travel what does it matter?

With the same servo arm?

in the same exact position? Some servos with same spline count have the raised part of the spline offset so it is in the same place as the low on another servo and 'straight up' on the horn is a half a spline different

I've noticed a slight variance between brands of servos as well, normally the range is close enough, but I can think of one time where I needed to use an aftermarket horn that had a little longer reach.. and it was a budget servo that didn't quite swing as far as most name band servos I have used.

Yes.

The one with 110-120 epa is a budget servo, the other one is a savöx

I just went through the same thing going from protek to a savox. the savox needed more epa then the protek did.