Which is better Canon A640 or Canon A710 digital cameras? Which cameras has the best pictures?

The A640 will produce better photos...but if you are only printing out 6X4 photos, then you might not necessarily see any difference. But I would still choose the A640.
The newer G7 has better image quality than those two, though.

I would say the A640. Okay, the A710 has image stabliization, but that's about the only advantage. And, the A710 zooms to 210 mm while the A640 stops at 140 mm (equiv.). The A640 sensor is twice as big as the A710. The A640 has 10 MP and the A710 has 7 MP. That's not a HUGE difference, but the points go to the A640. Tha A640 monitor flips out and twists around allowing you to get an "over the crowd" photo or to use an "on the ground" point of view. The A640 uses 4 "AA" batteries and the A710 uses 2. You would expect the batteries to last longer in the A640.

Go here and click "In-depth review" and "read owner opinions" for both cameras. Look at the sample images and draw your own conclusions. The larger sensor will probably do better at higher ISO's and in low light situations.

http://www.dpreview.com/reviews/compare_...

I'd buy the A640, personally. My son has an A620 and my brother has an A540 and A630 and they both like all of their Canon's.

easy answer
the a710is because it has image stabilization