For the last few months, we've been shooting with the two hottest cameras on the market. Lucky us. If you've been eyeing either one of these for purchase, here's everything you need to know.
Camera makers love to invent new categories. And while that can often lead to endless bloat, the Canon 5D Mark II and the Nikon D700 represent a sweet spot that had never been hit before—the semi-pro body with a full-frame sensor. And it's the category with the most bang for buck we've seen to date.
Yes, let's just get this out of the way: Both the D700 and the 5D Mark II give you more for your dollar in terms of features, image quality and overall excellence than anything else we've used. Period. We know not everyone is prepared to drop $2,000 to $3,000 on a camera body these days, but if you're thinking of investing for the long haul and, more importantly, have a good collection of either Nikon or Canon lenses, these are the two cameras you want to look at.
Why? Because they give you almost everything from Nikon and Canon's uber-pro top end for a whole lot less, most importantly the full-frame sensor (FX in Nikon parlance). With a sensor the same size as a piece of 35mm film, your old Nikon or Canon glass will produce beautiful results on these new bodies (assuming they're new enough to autofocus and couple to the cameras' meters). And if you don't have a collection built up already, your choices for new lenses will be significantly more exciting without the APS-C (DX, again, in Nikon's world) sensor's 1.6x crop factor changing their effective focal lengths.
The sensors in these two cameras are also responsible for their absolutely stunning high-ISO sensitivity performance—if you would have told me a few years ago that I could get 100 percent usable and almost noise-free shots in the dark at ISO 4000 with hand-holdable shutter speeds, I would have laughed in your Nostradamus-looking face. But that's the reality here, and it's awesome.
But of the two, which to choose? Now that's the question, isn't it. Here we'll share what we've learned from shooting with the 5D Mark II and D700, for work and for play, and hopefully you'll be able to make your own call.

Image Quality/Sensor

SensitivityAgain, both of these cameras will blow your mind with their high-ISO performance. Both go up to a ridiculous 25,600 ISO rating. The magic does not lie in their gaudy top-range though, which as you can see in our galleries below is still prit-tay, prit-tay noisy. No, the crazy thing here is that with both of these DSLRs, you can shoot at 3200, 4000, even 6400 in the right light and still have photos that look practically noise-free on screen. That's just crazy, and you can't accurately describe what this means to you as a photographer until you've shot your friends—handheld at quick enough shutter speeds—around a candle-lit table, and gotten photos that look absolutely gorgeous. Before, it took a crazy expensive lens to even come close to this, and even then, sensors (or even high-ISO film) couldn't keep up.

With the 5D Mark II and the D700, you're basically shooting with night vision. Like I was doing here at Snowscrapers a few weeks back. As you can see, there are floodlights, but it's dark. These guys are moving fast. But I can crank up the ISO high enough to pan with them without blurring them out, and grab stuff like this, without the sky turning into a snowstorm of noise.

Let's compare the high-ISO range of both cameras head-to-head, shall we:

5D Mark II ISO Range

D700 ISO Range

One big difference head to head in the imaging department is resolution. At 21 megapixels, the 5D Mark II has almost double the pixels of the 12.1 megapixel D700. As you well know by now, megapixels are not as important as sensor size/quality, but here, we're dealing with two evenly matched, high-performance sensors, both of them full-frame. So in this case, an extra 9 million pixels does give you something:

Interface/Handfeel/Menus

Here's where the Nikon vs. Canon flames start to get intense—both cameras take a decidedly different approach to menus and basic shooting controls. For me, I like a dedicated button wherever possible, even if this means the body is littered with switches and knobs of all sorts. This is the Nikon approach, more or less; ISO, file size, white balance, autofocus point selection, metering mode and even mirror lock-up get their own dedicated switches on the D700, which makes switching all of these things easier. On the 5D Mark II, all of these major settings share a button—press it, then rotate the thumb wheel to change one setting, and the index-finger wheel on the front for the other. I almost never remember which dial changes which setting, so that can be annoying.