Sharper at f/5.6: 50/1.8 or 18-55 IS?

Haven't tried this out for myself, but was wondering what the prevailing opinion is...

Let's say I want to take a photo, and for argument's sake, we're shooting a stationary object at ISO200, f/5.6, 1/100th, and the shot works out best at a focal length of about 50mm (or on my XTi, 50mm * 1.6 = 80mm, for the purists).

Point being: In the case where I'm using a smaller aperture (f/5.6, f/6.3, etc.) would I get a better shot using my 50mm/1.8, or my 18-55 IS f/3.5-5.6 at the 50mm focal length?

Just curious as to what you all think...

50 1.8 - it's well stopped down at that point. Wrong forum btw.

50mm...but i cheated
http://www.the-digital-picture.com …&SampleComp=0&F​LI=3&API=0

The 18-55 IS is really sharp at F5.6, except at 45-55mm. So for this instance the 50mm 1.8 wins. If you move to F8 on both, the 50mm still wins, but it is close.

Now compared to other lower end primes, the 18-55 does very well. 24-40 it the lens' sweet spot. So At 35mm, the 18-55 IS has nearly identical sharpness to the 35mm f2 at F4+. Same story at 28mm vs the 28mm canon primes.

And the comparison linked by DreDaze is somewhat invalid. One lens is on a Full frame 1DS vs a crop 40D. The 1DS Mk3 has much higher resolution, and that is what you are seeing mostly in the comparison. Comparethe two on the same camera, and it is not such an embarrassment for the 18-55 IS.

a prime is almost always sharper than any x-y lens