I prefer autofocus, and use that for 99.9% of my images. The only times I use manual focus are those times when autofocus will not work, such as when there is a heavy snowfall, in which case the AF keeps trying to focus on falling snowflakes, and doesn't "see past" them to focus on the subject.
Just looking thru the viewfinder, I cannot really tell what is sharp and what is blurry. The camera is much more accurate than my eyesight, so I trust it to do my focusing for me.
