There is something to be said for both schools of thought. Lets first examine each choice and determine the pros and cons.
The pack rack or expedition rack is a great idea for a couple of reasons, 1. It mounts the tent lower so you have a lower center of gravity. 2. It's open so you can access your gear easily, and 3 its light weight. This option provides an individual with many mounting options for a lot of things, like axe and shovel, high lift jack, lights and so on. The pack rack is generally suited to warmer dryer climates.
The cons of the pack rack is that your gear, though easily accessible, will get dusty or wet, thus creating the need for dry bags or water and air tight boxes that can be expensive.
The topper or canopy is a decent choice in its own right. 1. It's air and water tight if installed correctly, 2. It keeps gear relatively easily accessible. 3. It can host a slew of accessories if properly outfitted.
The cons, they can be expensive, they really need a rack system to mount anything correctly, and they add a fair bit of weight.
In the climate I live in, its wet A LOT. We get more misty and wet days than we get sun and it causes problems frequently with gear and camping. With that being said my topper was professionally installed and I haven't had an issue yet. With the proper drawer system this option can really be helpful. My gear stays organized, dry and dust free making for a very nice experience when I'm outdoors. Plus it keeps my fridge out of the weather and in great working order for whenever I need it.
Doesn't hurt to have a dry space for my dog either.
You really need to evaluate when and how you will be using it, this will make your choice much more manageable.
