Ken does actually have quite a good comparison of the two cameras put together here which is worth a read:
http://www.kenrockwell.com/nikon/d700/vs-5d-mark-ii.htm
If you're shooting landscapes or in other situations where you want absolute maximum detail retention, then yes the 21MP
does make a noticeable difference over 12MP. Even in situations like weddings, 10-12MP files might leave the fine details of the brides veil mushy, whereas 21MP files will retain them. To be honest, most of the time I do shoot my 5DmkII down in the medium 11MP mode since it's just kid/family shots mostly for computer displays, or if I do print some they're rarely larger than 8x12. No need for 21MP for that.
The Nikons do handle noise a lot better. The D700 doesn't have the low-ISO noise issues that the mkII does, and it maintains a cleaner noise profile to higher ISOs than the mkII does as well, although you can get equally good results from both. The JPEG processing is much better on the Nikon and it handles things like chroma noise a lot better and doesn't manage to mince details nearly as easily as the Canon will. I shot nothing but JPEG on Nikon, but the Canon JPEG handling is bad enough that for anything that matters I shoot RAW now and process through DPP myself and get much better results that way with my own NR and sharpening settings applied after the fact. Yes, the low ISO noise issues do need to be closely watched and handled as well, which is best done in RAW.
If ruggedness is a concern and you tend to beat your gear around, the D700 is definitely a better choice. It has a nice pro build and good weather sealing whereas the 5DmkII has more of a "good consumer" build and just basic weather sealing. A benefit of the Canon's cheaper build though is that it is noticeably lighter than the Nikon. A lot of Nikon shooters, myself included, have complained about weight, and that's less of an issue with the mkII and the Canon system in general I think.
Ergonomics is a wash. Just depends on what you prefer. I like that I can basically operate the Canon one-handed with all of the controls on one side. I think Canon has designed their cameras this way for all of their sports shooters who needed to support their super-teles with their left hand, and thus needed to be able to make all critical adjustments on the camera with just their right hand. The body controls are maybe a bit more complicated, but you can do most everything with one hand if you set it up right, whereas two hands are more often needed on the Nikons. Since I'm out with my kids a lot and needing to help or handle them, I do now prefer the easier one-handed operation.
Autofocus. Despite the mkII having a far less advanced autofocus system, I've actually never really had any trouble with it. It works fine for me, and most of what I shoot is my 2 and 4 year olds running around, sometimes with larger aperture primes at close range (aka thin DOF with moving targets). No issues, it works fine. With the 9 point system and the joystick on the back, you can instantly select any single point that you want so you're never scrolling, and then hit the button on the top to get it back into full auto selection mode. The only issue I've had with it is that the AF system does seem to quit on you about a stop or so earlier than any of the Nikons that I've had when the light gets low. To make matters worse, there's no AF assist light built into the camera body either so you're sorta stuck up a creek there. If low-light AF performance is a concern of yours, that's definitely a reason to strongly consider the D700. Even my D40's AF system kept running in lower light than the mkII's does. I consider this the only real "flaw" of the camera.
If you tend to mix up your type of shooting a lot like I do, as in action shots of your kids in one moment and then a nice colorful landscape shot in the next which of course requires completely different settings, the Canon is absolutely superior. Its C1/C2/C3 total recall banks work sooooo much better than Nikon's custom settings and shooting banks. Nikon has finally figured this out now, with the U1/U2/U3 setting banks on the D7000 which is said to work the same or better than the Canon setup at last. I'm guessing this will "trickle up" to the D800 when it arrives, and to other future Nikon bodies as well. For a primary body, I seriously could not live without a setup like this anymore. It always drove me crazy on the Nikons. I have C1 setup for landscape shots, C2 for my kids running around, and C3 for indoor flash photography. It makes such a huge difference because you only have to mess around with your settings once and then lock them it. It frees you to just shoot and not constantly jack around settings real-time.
Overall I'd say they're both equally good bodies, just different, and it depends on what you're looking for and your personal style of photography. The 5DmkII is going to be a bit more adept at some things, just as the D700 is going to be a bit more adept at others. My choice on going Canon had little to do with the bodies and mostly to do with Canon's lens lineup being much more to my liking, and this was the entry full-frame DSLR body that Canon was offering so that's what I got. I like how this Canon body works a lot, but wish I could put the D700's sensor in it. I don't really need 21MP most of the time, and it would free me from having to screw around with RAW files nearly as much since the D700's sensor handles noise both at low and high ISO a lot better and looks great straight out of the camera in JPEG. :smile:
