Aside from the approximately $75 street price differential, the real distinguishing element between the two is the photo quality. In general, both produce colorful and crisp photos, with relatively little fringing or distortion. Fine details showed up clearly in our test shots, though colors tended to appear slightly muted and cool. The A630 displays a bit less noise, however. Artifacts start to appear at ISO 400 and become a fine but visible grain at ISO 800. Images are still usable at ISO 800 for 4x6 prints but aren't as sharp as photos taken at lower sensitivity settings and display problems with color banding.
Though the A640 continues the PowerShot's history of less-than-stellar low-light shooting, it's otherwise a great camera for users who want a solid point-and-shoot with photographer-friendly manual capabilities. But unless you really need the A640's extra pixels, save yourself a few bucks and get the A630 instead.
(Shorter bars indicate better performance)
|Typical shot-to-shot time||Time to first shot||Shutter lag (typical)|
(Longer bars indicate better performance)