While the VTX (1300 or 1800) are great bikes, they are, at their core, cruisers and not touring bikes. Like any bike, they can be used for touring and can be modified to be better at touring but this does not make them ideal touring bikes. In their stock forms, some of the features they lack that would make them better touring bikes and which most/all modern touring bikes have are:
-Wind protection via fairing and some form of lowers
-Music and sometimes GPS
-Lots of storage space in saddle bags and trunk
-Large range - at least 200 miles at highway speeds - 1300 can reach this but not the 1800
-Comfort in the seats and seating position
-Cruise control - not a throttle lock but a true cruise control
I have ridden VTX bikes and have toured on cruisers (VTX and HD Softail). I have also done a fair amount of touring on a true touring bike (Victory Cross Country Tour). The difference is very significant. Even when a VTX is modified to make it a better touring bike, it is not as good at this role as a bike designed to be a touring bike.
Please do not misinterpret the above discussion as me disliking the VTX line of bikes. I think they are great. My point is that there are "horses for courses" and for touring, nothing beats a true touring bike.