I've owned the 18-55 IS and the 50 1.8 II. The 50 1.8 should beat up on the 18-55 IS badly. I've also dropped mine in a river and cracked the front element, and it's still razor sharp.
You may need to MFA the prime.
I continue to use mine, and am always thrilled with the results. Very sharp and fast.
Your first image is in nice light. The second image looks like harsh light, and there's all kinds of trash laying around. Is that a garbage dump in the photo? The second photo also looks out of focus. Try another copy if it happens consistently.



