Update.
I thank everyone's opinion and it was a tough call. The bottom line is that folks are happy with either one of the cameras. So I figured I would not be going wrong with either one.... and it is an upgrade from the A70.
The A70 Canon housing has made quite a journey..... The Tuama
otu Atolls of French Polynesia, Hawaii, Cozumel, Roatan, Belize, La Paz, and of course, Catalina and San Diego. The housing flooded only once in approximately 110 dives and that was pure and simple my error. I did not clean the o-ring prior to a dive. When I needed a replacement I just went to e-bay and picked up another camera. The only reason I am replacing the A70 is that it is now acting funny in the water, but when I get it on land it works perfectly. So it is upgrade time.

I found an A710IS on e-bay for a buy-it-now price of $172.00 in its original box. I'm not even sure it was used it was because all of the cables were still wrapped. I have had it now for a week and I have been happy with it and still trying to learn all the bells and whistles on it.
For the most part, we who take pictures underwater, are not professionals, but want to have momentos of the wonderful creation underneath the surface of the water- a creation that I consider divers are especially blessed to see.
The next time I upgrade is when I can look at an object, blink my eye and have that picture recorded and printed by the time I get backt to the boat. Far-fetched? Maybe? Maybe not? Forty years ago we had cutting edge technology. It was called the 8-track tape, now we have the Video iPod with 80 GB hard drive. We've come a long way.... and it's still changing!
Thank you all for your experience, help and opinions. They really mattered to me and I am really glad I rediscovered the ScubaBoard.
John