I strongly disagree with iGas.
You will get used to the grip of the camera and how it feels in your hand eventually. You can't get used to sub par images. And it's lenses where you should spend the good money on rather than getting mediocre lenses which degrade quality.. why? Good lenses can last 30-50 years. Cameras will eventually become obsolete and be replaced but good lenses are forever.
I recommend trying the best lenses in store with an image card or 2 and going home and comparing the quality of whatever he's happier with.
f/2.8 lenses are better than f/4 lenses. A 24-70 f/2.8 is the best normal zoom money can buy but it tends to be a little too heavy for most pros. That's why we tend to break it down and get primes like 28mm f/1.8G, 50mm f/1.8G, 85mm f/1.8G. Just switch the lenses around when you need to change.
But if you have to compromise and want a f/4 zoom.. a Nikon 24-120 f/4 is awesome. Infact it's better from the 24-105L. I tried them both before I went Nikon and my findings were video canon is better but images Nikon is way way better.
I agree Nikon produce better still than Canon dollar for dollar at the moment, however I'm sorry to bust your self proclaim "pro" buble that the Nikon 24-120 is not better than Canon 24-105L (and please provide links to backup your claim). And, I still stand firm on my opinion as cameras bodies has to be comfortable in your hand to use.
I agree that many people tend to go with prime due to weight (pro and non pro), however people who go with primes also look for IQ and fast aperture, and they tend to have more than one bodies hence it is just as versatile as zoom. And, unless pros are little girly men...I do believe that many wedding photographers and perhaps fashion photographers loves the 70-200mm f2.8 zoom that is quite heavy to complement their prime lenses, and it tend to be use much more than the primes because it is versatile.
The 24-120 f4 suffers purple fringing, ghosting, and flares, and it is fare worst than the cheap Nikon AF-S 24-85/3.5-4.5G VR in this category.
http://www.cameralabs.com/reviews/Nikon_Nikkor_AF-S_24-120mm_f4G_ED_VR/
DxOMark review for the Nikon 24-120, the new constant f/4 aperture on DxOMark.
http://www.dxomark.com/index.php/Pu...rture-on-DxOMark/So-who-is-this-lens-good-for
Given its price and specs, this lens belongs to the high-end category. As such, one would expect better performance, especially when mounted on full-frame sensors. Indeed, it is a shame that one has to use this lens at 5.6 to keep chromatic aberrations and vignetting low.
PS. I do not own the Nikon 24-120, but I can speak for the 24-105L because I own it, and it is a damned good lens for a kit lens, and IMHO the 24-105L is just about as sharp as my 50mm prime in the center, but slightly softer than the prime at the edges.
<-- I have owned and use perhaps over 30 cameras in the last 25+ years, and it include Minox 1/2 frame, point-n-shoots, 35mms, medium formats, large formats, to 20"x24" Polaroid.