No, you are not overlooking anything.
Even the reviewers didn't even take a second look at the A610. They reviewed the A620 and said "why review the A610".
The only real difference is the megapixels.
With the prices being so close, why not take the A620.
If you plan to do some cropping, it is nice to have the extra megapixel.
I'm a digital novice getting my first digital camera. I plan to use it mostly for snapshots (especially for an upcoming trip to Europe)but, as a former aspiring pro in my youth (a long time ago)I can see the possibility of getting the itch to do some enlarging and cropping. Both the Canon A610 and A620 sound like they would be adequate for me, the only difference I can see being a higher resolution (7 vs 5 Megapix) and slightly higher max shutter speed in the A620. In shopping around I find they're both about the same price (at one store $1.00 difference!). It would seem to be a no-brainer to chose the A620, but I worry that I'm missing something.