The biggest negative with the LHT is for the height-challenged, as the 54cm version and below uses a 26" wheel while the larger versions use a 700c wheel. They do this for the sake of toe clearance because of the geometry that they use.
Any dedicated touring bike will tend to have longer chain stays and a longer top tube (Trek 520, Soma Saga, LHT, etc.). That said, the All-City (Space Horse) is more of a middle-road bike built for commuting and would be closer to a Surly Cross Check or Pacer (geometry wise). Other bikes built along the same lines as the Space Horse would be a Jamis Bossanova, or maybe a Kona Rove (which shares the frame with the Kona Sutra touring, but is built up as more of a cross/gravel bike).
There are a bunch more examples, but that is what comes to mind.
You might find this useful:
http://www.adventurecycling.org/adventure-cyclist/online-features/touring-bike-buyers-guide/
As far as a nashbar vs a LHT, I'd have to pull up the sites and compare numbers... might do that later. Generally speaking, besides geometry, a frame is a frame. Pay more for lighter weight tubes, frame warranty, paint&finish.