A fully reusable system is only an advantage if it cheaper than a expendable one. At several hundred million dollars a launch the shuttle is more expense than using a "big dumb booster", it make no difference if the shuttle itself is reusable.
The shuttle system
is not reusable. the shuttle is, the tank is not, and, contrary to popular belief, the SRB's require so much refurbishment per use that it would be cheaper to reduce cost through just mass producing them.
The cost over-runs on the Ares system are mostly due to the falling value of the american dollar, not any inherent defects in Ares.
You need to read about some of the problems with Ares before you make a comment like this. Try the Forums on WWW.nasaspaceflight.com
for some good reading. Most of the posters there are space industry engineers including alot of nasa employees.