- Both are known system.
- Both can meet the missions for lifting cargo now.
- Both were developed to meet DoD AND NASA's needs for cargo.
- New development would be limited to safety margin and abort warning systems. A trivial amount to the Ares I.
Also, the only thing Ares one has in common from Shuttle is the casings from the SRB's, the nozzle actuators, and the actuator power train. The hydraulic actuators are scheduled for replacement with eclectic actuators anyway.
The rest is new... So much for reuse; which Congress mandated by the way.
There is a good argument for Ares V, but I'd look at Direct 2(Jupiter-232) as an alternative since it makes use of at least 50% current shuttle components.
In direct contrast to the current Ares Launch System (ALS), the Jupiter Launch System (JLS) reuses most of the existing manufacturing, integration and launch facilities of STS, as illustrated in figure 2. Because all the new technology requirements are moved to the lunar exploration phase of the VSE, NASA can focus initially on fielding a significantly safer launch system than the Space Shuttle, yet one which is far more capable than the Ares-I. With more than double the lift capability of Ares-I, the first Jupiter Launch System (JLS) variant enables the Crew Exploration Vehicle (CEV) development team to deliver a fully lunar-capable vehicle to NASA, unconstrained by the current limitations of the Ares-I. In addition, this first variant of the JLS, the Jupiter-120, has enough excess capacity to complete the ISS, thus obviating the painful decision of leaving finished ISS elements on the ground or retiring the Space Shuttle on schedule.
Amazing what engineers can do when you leave the bureaucrats out of the equation.
I like the idea of using existing components in a new configuration to "git'r done", and not leave us out of the game for so long.
Remember when this country used to have the "can do" spirit?