From someone who switched from Western to Eastern Arc only a year ago, I can tell you that the picture on eastern arc looks "crisper". It is not artifact-free, but it is more pleasing to my eye, especially on black & white programs and those shot in low light situations. Blues are truer. Reds noise-free (not artifact-free). And an hour-long program only takes 45 to 50 minutes of time as measured by my 622 receiver.
This applies to HD channels ONLY. I did not do a detailed comparison on SD channels when I switched. The tests are completely subjective, done via HDMI input on an Hitachi 42" Plasma TV