I have two LHTs, one rim and the other disc brake. Buying new I would go with disc for these reasons:

1. no rim damage from brake pads so wheels may last longer
2. easier to remove wheels if using wide tires since wide tires may not fit through opening of rim brakes (I experience this often with 2.15 tires)
3. also easier to remove wheels in general
4. no canti- or v-brakes, cables, or housing to interfere with installing racks, lights, etc. at fork and seat stays
5. replacement brake pads smaller so less room and weight to carry spare (more room and weight if one carries spare rotor)
6. disc seem to handle loads better on downhills than rim brakes (which is why I bought disc LHT)
7. if rim out of true, does not affect braking
8. adjustment of brake pads seem a bit easier with bb7 than with canti- or v-brakes

Some possible drawbacks I have noticed

1. installing wheels sometimes requires adjustment of disc brakes especially in front wheel - slight difference in wheel placement can lead to rubbing of disc pad
2. disc version of bike usually heavier due to extra material needed to support fork, brakes, rotor, etc.
3. rotors can be bent or out of true
4. if going remote, disc components may not be available in some areas whereas rim brakes are commonplace
5. if packing bike for travel, may need to remove rotors to protect them from damage