I also have had both. The CIPA straps will decay with age and I would have to replace the mirrors about every 1.5 to 2 years; I never found any replacement straps so I'd end up buying the whole unit again. Other than that I had no problem with them staying on my Highlander.
So then I tried an Aero. They worked also, but the gap between the vehicle's mirror and housing was too small (about 1/8" gap at most) to allow the OEM mirror to move properly. In other words, the clamps on the Aero would intrude too far and bind the OEM mirror in an unnatural position, rendering that mirror about useless. I didn't have this problem with the CIPA, so the latter remained my preferred mirror. I'm sure it's a problem that not every vehicle mirror would have, though. On the Lexus GX I just bought this month, the housing-to-mirror gap is more like 1/4" and the Aero should work fine.