I'm really looking for an overall performer camera, so definitely handling and autofocus speed can be critical at times.
handling for both is fine. AF on the 5D is fast and accurate with the center point, even in very low light. i imagine the D700 is the same. i don't have personal experience with outer points on newer Nikons, so i can't speak for that. 5D outer points are useless in low light unless there is clear contrast at the point you are focusing on.
I hadn't really given a lot of thought to high iso performance, but that also is a big factor for me. I used to push film often in my black and white film days - lots of times even f/2.8 can be a bit slow.
keep in mind that digital is
much cleaner than film, although noise isn't quite as pleasant as grain. higher-end SLR noise generally looks more like grain.
My main gripe with digital so far has been the lack of low-light performace overall, and highlight clipping in contrasty situations.
not sure what you mean by "lack of low-light performance." highlight clipping has to do with dynamic range, and you'll have the same issues unless you get a camera with 9 stops of DR, not including highlight/shadow recovery (which boosts the DR by a stop or so in the highlights). according to DPReview, the only SLR i know of with that kind of range is the 40D. outside of that, you need MF, or live with the blown highlights and just recover them in post-processing.
Also, I will be doing some personal projects (b/w environmental portraiture, landscape, etc.) but... most of my projects will fall into the photojournalism category - multi-photo series/features on various subjects, minimal (but possible) spot news, and travel/tourism subjects (people, activities and places.)
based on that, i don't believe the 5D AF will hold you back. and for the record, the 5DII's AF is not exactly the same as the original 5D. it's a little bit faster, at the very least, with the center point. what is the same is the poor outer AF points, which aren't cross-type like...all the other SLRs Canon sells now
On the Nikon side - the 14-24 f/2.8 lens has gotten some great reviews, and I've been eyeballing it a lot. I guess what I'm wondering is how important it is to be as wide as 14mm when going FX? Is it too wide for a general walkaround wide-angle. One thing is the 14-24 doesn't overlap the 24-70 but I'm not sure if that matters that much with the 17-35 - it might stay on the camera longer.
first, remember the 14-24 is huge and hugely expensive. as for how "important" 14mm is, it's not any more or less important than any other focal length. it depends on your shooting style, so only you can answer that question.
overlap shouldn't be an issue. if anything, it's a good thing, since you won't have to switch lenses as often (unless you rarely use 24mm)
and on the Canon side, there's a 14mm prime, which, according to its users, is sharper in the corners than the 14-24 is in the center (at 14mm).
On the Canon side - the 24-105 f/2.8L looks like a real handy lens - a great overall range for general use. And the 70-200 f/2.8 is a classic 35mm format lens, where I've read the Nikon 70-200 f/2.8 was better suited to DX sensors and a bit soft on the edges with the FX format.
there's only a 24-105 f/4. if you want f/2.8, it has to be a 24-70.
on Nikon lenses and DX vs FX sensors: for a long time, Nikon intended to stay with DX (APS-C) sensors. as a result, some of their lenses were optimized for cropped sensors, and work the best on DX cameras. Canon, meanwhile, always designed its lenses with 35mm sensors in mind, so they can be a bit lackluster on APS-C, but "come alive" on 35mm. BUT, that doesn't mean the Nikon 70-200 isn't close the Canon in IQ.
It's a lot to contemplate, but I'd like to get the best glass overall, regardless of whether it's Canon or Nikon.
in that case, you'll have to pick out all your lenses before you buy anything. i wouldn't bother, unless one company doesn't have a good lens at a focal length (range) you want.
One last question to post to you guys/gals: What are the gems lenswise in both Nikon and Canon's lineups, either new or classic lenses between 24mm and 200mm - primes and zooms.
for Canon, the best lenses are the L primes. all the "L" lenses are great, though. the top-notch primes for their focal lengths are:
14/2.8 II
24/1.4 II
85/1.2 ("legend" status)
135/2 (ditto)
200/2 (also the sharpest lens Canon makes)
for zooms:
17-40/4 (for the price)
70-200/4 IS (closest you'll ever get to fixed-focal IQ in a zoom)
The shooting flexibility you'd get from the ISO performance of the D700 way outstrips the cropping flexibility you'd get from a 21 mp sensor.
the difference in noise handling between the two is close enough that it doesn't matter.
Not to mention the vastly superior focusing system of the Nikon.
the Nikon is only "vastly superior" at tracking, particularly when not using the center point(s).
