xnihilo, I can only describe the difference between a touring bike and a mountain bike.

Both have fairly long wheelbases though the touring bike's is longer. The touring bike has more of a tendency to go straight with a bit more effort to initiate a turn, which is to be expected. The mountain bike isn't exactly 'flickable' on pavement either.

For me, one has drop bars, the other flat handle bars. Trekking handle bars have as many or more hand positions than drop bars and are becoming more popular for those who prefer flat bars.

A front suspension isn't needed on the street and if yours doesn't have a lock out and not a lot of dampening, it will eat up some power and make loading the front more complicated, although there are work-arounds for the latter.

I used my mountain bike for some short trip touring before I bought a touring bike. I love the way my mountain bike handles technical trails and didn't want to change it for another role, I did leave the rear rack installed as it would be perfect for touring on unimproved surfaces and is handy for carrying food and such to remote areas.

Another possibility for you to consider is to buy a fully rigid mountain bike from the '90s. Many bicycle tourists have followed this route and are happy with the result. The cost, even after outfitting it for touring is often less than a bare touring bike bought new.

Brad