I think it is entirely personal choice. Primes don't meant having to zoom with your feet: you don't have to carry just one prime.
My personal choice is to use a few lightweight primes. My reasons are high IQ across the frame, light weight, bright viewfinder and easy balance on the camera. If I'm travelling light I'll have a couple of Lowepro cases on a belt with a couple of lenses.
Primes also mean that you use a proper hood for the focal length, which for me, as I'm often shooting across or into the sun, is beneficial. The 24-70 f2.8 mark one had a very clever system of a long hood and the longest focal length is the shortest physical length; thus the hood matches the focal length. However on all other standard or wide zooms this isn't the case. On my 24-105L I have a Hoya rubber hood which you can squash in for 24 mil and pull out for 105. This is a major improvement over the standard, wide angle hood. The 24-70 f2.8 II is an 82 mm filter and I don't think anyone makes one like that for this lens, so for me that is an issue.
Also because I'm mainly producing stitched images I don't use an ultra wide angle lens. 28 mil is as wide as I go, so I don't really have a vast range requirement. I suppose in summary, if we are talking about landscape photography where you are trying to resolve tiny detail that is a long way away, a 'standard' range on FF, if you want to make every pixel count at all the focal lengths of a zoom,( not just the one focal length and aperture combination where it may be excellent) you have to go for the 24-70 f2.8 II. As this is a heavy lump, and you cannot hood it properly at mid to longest length, I prefer a few high quality, light primes, and the 24-105L as a fall back position.