epp, we have to disagree about Canon's layout.
First of all, what do you mostly adjust when you're shooting? For me it's shutter, aperture and ISO. I rarely switch modes during a shot. I rarely switch WB during a shoot (I'm a portrait/artistic shooter, not a photojournalist). I rarely shoot in AI servo, I shoot almost exclusively in one shot mode.
As my video shows, all of the buttons I need to access are immediately available to my right hand without any assistance from my left. When I want to quickly bump the ISO while shooting my Canon, I don't have to remove my hand from the lens where it rests naturally and adjust it in what I feel is an unnatural position. Putting both hands right next to my face unbalances the camera and is awkward to me, which the Nikon system forces. I would instinctively remove the camera from my eye to change the ISO as it's oddly placed on the left side of the body.
To change the focus point on my camera, I don't have to go into any menus. I tap a button with my right thumb and rotate the index finger wheel to select the point I want. It's fast, easy and intuitive. My FEL button is also intuitively placed by my right thumb as is the AF-ON button, which I do use.
Having the WB and metering mode selection on the same button doesn't seem odd at all. They're as relevant to each other as the shutter and aperture are. To me it's not confusing in the slightest and I like the system. I prefer 3 buttons to 6. Nikon is cluttered with buttons and switches all over the place. If you have a hard time remembering what 3 buttons do, how do you remember what 6 do and their placement? Seems like a moot argument to me. Regardless, I don't often switch my WB settings in the middle of a model shoot, nor do I switch metering all that often. I do change aperture, shutter and ISO all the time, and as noted these are very conveniently located unlike the Nikon system where these critical controls are on two sides of the body vs. within reach of one hand or finger.
I want my power switch out of the way, I don't want it under my shutter button. That location makes little sense to me. I don't turn my camera on and off 50 times during a shoot. I don't want my camera off when I need it on. I don't want to accidentally turn it off. I like it being a very positive yet recessed switch that I use twice during a shoot. I turn it on when I start and I turn it off when I'm done.
For me, and what I shoot and how I shoot, the Canon system is far more comfortable and easy to use than the Nikon system. I've given the Nikon system two chances in the past to win me over and twice it failed to do so.
I also have very large hands and the cramped Nikon grip/shutter placement is very uncomfortable for me. The shutter release points darn near straight up on a Nikon which is uncomfortable and unnatural for me. I like the more angled/sculpted position of the Canon system. Holding a Nikon with my finger on the button causes unnecessary tension in the joints of my index finger.
I also find the Canon index finger wheel to be perfectly located, but then again I'm 6'5" and have huge mits. Perhaps someone of smaller stature wouldn't find it as comfortable as I do.
It's all a matter of perspective and preference.