I bought the Canon 10-18 a couple months ago, and so far I really like it. Canon didn't put a lot of money into the lens body, but they seemed to have put it into the glass in this lens.
The 70d will allow you to display the focus points the camera used when you view the pictures with the cannon software. Turn this option on, and retry your tests. If the focus points are not the same, you really are not shooting the same picture each...
