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You'd want a lower trail on a loaded touring bike, no? The front weight would offset the lighter steering.
Lolo-
From the article:
So a touring bike might have a lot of trail to provide a stable, predictable ride, while a race bike might have a small amount of trail to offer quick, sharp cornering
I did say 'too much'. Loaded up you're likely to be going slow uphill, and you don't want to be fighting to keep the bike in a straight line when climbing and tired. Large front load and low trail will exaserbate wheel flop at slow speeds.
Edit: that's only half the story actually. Here's a good article on it, your HT angle plays a part.
With a front load, you need a very different geometry. Because the load turns with the fork, it has two effects. At high speeds, the inertia of the load tends to stabilize the steering so you decrease the trail to make the bike more nimble. At low speeds, the load wants to rotate around the inclined steerer axis so you also steepen the head angle to reduce the force the load exerts on the steering.
tl;dr just ask Scoble
Polygon
Neither, it's just a factor in the resultant trail. Measure your forks offset by lying them on a flat surface and use that calculator.
If you're mostly going to be on road I'd guess matching your current fork plus a bit more offset probably isn't a bad plan. You don't want to reduce trail to much though, especially on a tourer as it'll make it more unstable at low speed.
http://www.cyclist.co.uk/in-depth/816/how-does-frame-geometry-affect-a-bike