Aperture vs Image Quality

I am posting the question because I notice I get better IQ at higher
aperture settings with my Olympus E-520 with 70-300 or 40-150 lense.
F 8.0 with my 70-300 gives good sharp results.
So is it best to use Aperture priority or Manual mode for most shots ??

Thanks in advance

Most lenses have a sweet spot. I usually shoot around f/8 or f/10. Aperture priority or manual makes little difference with IQ and has more to do with exposing the shot right. Aperture priority will work most of the time but if the lighting isn't perfect you may miss the shot.

Aperture priority is a significantly more useful mode than any dummy or auto mode.

Manual mode is best for unchanging, or slightly changing environments, its also the only mode I will ever use with a flash. But I rely mostly on priority modes in frequently changing scenes, when I'm out shooting casually. With smart use of exposure compensation, and spot/center metering + auto exposure lock, it can give you a pretty comprehensive control over the exposure.

It depends on what you are shooting. Most sports require a high shutter speed so Shutter Priority, but Micro-photography and Landscape photography your better off using Aperture Priority, and also with Micro-photography I use manual focus.

Thank you for all the replys.
I was out to a car show last night. I took some pictures of my GTX
using Aperture Priority. Again Cloudy skies , sun was going down.
I had good luck with F 8. Because of the dark conditions the shutter was 80 - 100.
For now I will mainly use Aperture Priority ( For stationary objects )
I like the way the camers adjusts the shutter according to lighting conditions
The origional is better then the re-sized image below