Both/and, not either/or
I don't know any professional astrologers who have thrown away their ephemerides just because they have good computer programs. The tools are used differently. With an ephemeris, you can scan for trends or configurations much more rapidly than you could scroll the same material on a screen.
There is an issue of accuracy, however. This issue was addressed quite clearly in the Introduction to The New American Atlas for the 21st Century – Michelsen Memorial Edition (
http://www.starcraftseast.com/). The accuracy of planetary positions is based upong several factors, but one of the most important is which set of equations to use. The Jet Propulsion Laboratory (JPL) periodically revises these.
Another accuracy issue involves planetary stations. When a body slows down, the math gets worse. Just what is the exact point of the retrograde? Most of the programs on pc's are not capable of calculating the correct instant, so another question is whether the program then relies on tabular data to increase the accuracy of this component.
As more bodies like Eris and the asteroids engage astrologers' interest, the issue of accuracy becomes greater. There simply isn't as large a body of hisotrical data to work with, so the equations will change more rapidly.
