I agreed with all that Cycco, and:

There isn't one correct answer to this question.

The standard is a rear rack. Someone wrote an article decades ago, probably to promote lowriders which were an oddball format back then, and came up with some tripe on why lowriders and front placement were better. Obviously low CG and a better weight distribution is orthodox, and a comon objective, in say, sports cars. This has now become gospel amoung techies, but the main problem with the theory is the effect of front racks on steering and road feel. It takes quite a lot of gear before I even notice the presence of a rear rack load. A camera is enough to make it'self felt on a front rack (not negatively). For light loads I always use a rear panier. Actually a heavy front load can suppress a lot of raod shock and that is high on my list.

Individual bike geometry makes a difference for instance the rear rack placement will have a lot to do with whether the rear rack weights or unweights the front of the bike. Trail will have a lot to do with how a bike handles with a load up front. Some bikes love front weight and others are dangerous with it. Some of this can be dealt with through custom racks, but that isn't an option most will embrace.

http://kogswell.com/testPR.pdf

There are also convenience issues as far as what happens to a loaded front wheel when you try to park, which may explain the front rack kickstand:

http://slbike.com/e/index.html Under accessories.