The A610 in my mind is clearly the better bargain. Considering I was able to get these pictures on this page with the A75 and that only has 3mp, trust me you will be fine with the 5mp A610. http://photography-on-the.net/forum/...=123208&page=2 (Scroll down there are 4 of them)
Really the only major things that an A620 has over the A610 are the 2.1 extra mp and the remote option, and unless your really anal about the colors I guess that could be a "perk" too. Oh did I mention you'll be spending about $75-100 less too, so with that extra money you could pick up some things that'll help you along the way, such as a small tripod, cleaning kit, camera case and a nice sized SD card.
Just making you aware of your options.