Manual Focus versus autofocus

Does the manual focus makes the image sharper ?

not really correct. the Autofocus system might struggle in the early time when it was introduced. but, now, with more modern chip inside the camera the differences is nearly zero. we hear word 'cross focus point' and 'focus point' in autofocus sytem. some folks said that cross focus point is better than 'focus point'. Nikon d90 has 1 cross focus point placed in the middle and another 8 is just 'focus point'. some folks say that cross focus point has more sensitivity than ordinary focus point. in d700 all of its 12 or maybe 18 focus point are 'cross focus point'.

Is manual focus faster or slower ?

it's an reasonable question but a silly question one. lol. 

focusing on an object depends on practices. practices makes perfect faster. if you're a novice using manual focus perhaps takes more time. but in some conditional below, i guarantee that manual focus seems faster than autofocus : 

1. there is a barrier in front of object you want to shoot. for example a bird or lion inside a cage.

2. night...based on my experience using d90, autofocus seems struggle when there is only a dim of light.

3. object that moves fast and unpredictable, for example little child under 5 who moves so actively.

but, luckyly in nikon switching between manual and autofocus is very fast and easy. 

you can change it by switch the button in the lens. all new lens of nikon has this switch.

M/A mode = manual automatic (it gives you a chance to autofocus but you still can rotate the lens to achieve the best focus you want, although sometimes after you manual focus it will 'overwritten' by its autofocus)

M = manual (100% manual), practices makes perfect faster

M mode

M/A mode