I recently had the chance, though inadvertently, to test this hypothesis, when I bought a Tubus Fly rack that I intened to put on my Bottecchia, which I did.
The Bot, however, has a lower-trail fork, being from the late '70s, when that was the convention. And, oh, she handled horribly with a load on that rack!
So this weekend I put it on my Fuji high-trail bike instead, threw several pounds of vegetables from the Farmers Market and a couple of U-locks in it, and--voila! Smooth as can be!
I'll try a front rack on the Bot as soon as finances allow.
Since load-carrying is an important part of transportational bicycling, these differences are significant--a miserable ride will make it less likely that you use your bike for transport. So here's a rule of thumb:
If the front fork of your bike bends or angles forward only slightly from the crown, you probably have a high-trail geometry, and will be happier with a rear rack for carrying loads. A front rack will make the bike feel sluggish and heavy.Saddlebags (which hang from the back of the saddle) work well on any bike. These require a saddle with little loops for attaching the bag, though there are various devices one can buy for attaching themn to a saddle without loops.
If the fork curves farther forward, you probably have a low-trail geometry, and will be happier with a front rack for carrying heavyish loads; a rear rack will make the bike feel wobbly.
Lowrider front racks, which carry a pair of panniers centered on the front axle, also seem to work well on any bike, though they look a bit ungainly.
Either way, you can carry remarkable loads on a bike with the right rack and bag setup before having to resort to a trailer.
We'll have more on this subject in a full-fledged article later this year.