I would think that it would be noticable on all the surfaces.

With my old Hitec analog servos on all surfaces, you could easily see the poor centering on all the surfaces. It made the plane hard to fly- (Sig Cap 231 EX ARF). The plane was always rolling one way or another and I was constantly making pitch adjustments with my trim tabs in flight. Landings were difficult, because the rudder would be slightly off center and it made the plane track funny on final and on the runway.

The coreless JR servos come back to center perfectly everytime . Maybe not perfectly, but it's about as good as I can see with my eye and a control surface throw meter.

The JR digital 8411 is superb. My rudder comes back to the same spot every time, with no "hunting" around the center. It just comes back, BAMM!! and on center in the blink of an eye. I love it.

I am going to run a coreless servo on my throttle too. I think that it might help me to "feel" the hover more. If your throttle doesn't move the same amount every time and it can't find the same idle on every landing, it could make your engine difficult to manage.