Several guys in our club that have a combination DD/trailrig swap tires. Really aggressive tires such as Swampers rule on the trail around here because of the mud, but obviously suck on the street. It's also cheaper in the long run because a bias Swamper will only last about a year (depending on how many miles of course). Here are the choices as I see it:
1. Run Swampers (or equivalent) all the time, replace them every year on a DD, live with poor street performance but do good on the trail.
2. Run something like a radial BFG mud tire, and compromise both street and trail performance (again, this depends on the local terrain....around here it's always muddy).
3. Run two sets of tires...something like all-terrains for the street, and Swampers or equivalent for the trail. No compromises in performance. The trail tires will last for years, and some radial all-terrains will last at least twice as long as Swampers.