Esto dice la información de canon:

Ef SERIES (EOS 40D, 50D, 60D):
-Ef-A Standard Laser Matte focusing screen.
-Ef-D Precision Matte surface with etched grid lines.The camera’s AF points remain fully visible.Focus characteristics are suited to mostlenses.
-Ef-S The Super Precision Matte focusing screen isoptimized for wide-aperture lenses from f/1.8thru f/2.8. Areas that are slightly out of focusappear more out of focus, making it easier totell when focus is right-on. It is ideal for userswho frequently use manual focus in dim lightwith fast lenses.
Y los precios a día de hoy:

-Ef-S: 34,95$ (29,50€). Para enfocar con grandes aperturas.
https://www.amazon.com/Canon-Focusin.../dp/B000X02ARI
-Ef-D: 44,42$ (37,49€). Con cuadrícula, para líneas o autoenfoque selectivo.
https://www.amazon.com/Canon-Focusin.../dp/B000X06ZH4
-Ef-A: 13,78$+5,22$ (16,04€). La que trae, pa' porsi...
https://www.amazon.com/Canon-Focusin.../dp/B000X04B52


Muy buen tema. Yo tiraría por una tipo D, para mis gustos...