I bought a 7D a while back over a 5D II and my main reasons at the time were the more advanced autofocus system plus higher fps. I'm an amateur but now I'm finding myself more confident I rarely take the camera out of manual, tend to meter based on a point of interest and for focus just about always use spot towards the center of the frame and recompose.
I've seen some complaints about the 5D autofocus but I'm guessing they are mainly about the lower number of focus points and less cross-type. Anyway I guess my question in general is from anyone that's used both would spot AF be noticeably different on either body? All my lenses are f/2.8 or faster, but sometimes I do take some photos in low-light conditions without AF assist where the 7D does hunt a while.
I own both and here is the breakdown. The 7D's autofocus is much more advanced. Does this matter for portraits and landscapes (non-moving subjects)...probably not very much. With both bodies, I have set them so AF doesn't engage with a shutter press, but with the AF On button. On the 5D, I almost always have set to the center point only, and press the AF On button 2 or 3 times when shooting in a situation that makes good AF difficult. For my taste the center point is too large, which brings me to the one real advantage of the 7D when talking about non-moving subjects...enabling the smaller, precise center point that is disabled by default. It offers a true pinpoint for focusing on small subjects that may be behind something larger (squirrel face looking out from behind a fork in a tree branch). In this case, the 5D or the default center point on the 7D will want to focus on the foreground object.
When it comes to sports or moving subjects, setting the 7D to use the 9 center points and AI-Servo, will blow away the 5D on AI-Servo. The 5D is still not bad in this area, but it is much harder to keep the focus on the moving subject...you really have to concentrate. For sports, you should definitely set the AF to start with shutter press.
The Too Long Didn't Read of all this is: 7D has better AF than 5D Mk II, but the 5D Mk II's AF is plenty good. For me, the image quality of 5D is more important than the slightly better AF of the 7D. UNLESS, I am shooting sports, then I grab my 7D every single time and set it to 8fps, 9 center AF points, and AI_Servo.