The design for ITER was finalized in 2001, amended in 2007. Construction for W7-X started 2003. W7-X is now built, fully functional and operational. At several points during its construction, the construction process for its required parts had to be invented first.

That's 15+ years of research, breakthroughs and inventions in plasma confinement physics and engineering that have had to happen first.

As a noncommercial research reactor, W7-X will continue to be useful for many years to come. For material testing alone I would imagine access to reactor capable of producing a stable, continuous fusion reaction is invaluable.

The ARC is a design proposal from 2015. As such they have access and can utilize all the achievements, results and processes from W7-X, ITER and other material science advances of the last 15 years. If their proposal was not better than already built specimens, it would be a bad proposal. To declare it a race against the research foundation they built upon seems ignorant at best.

In 10-20 years, when the ARC is built, a new design proposal will emerge, based on even newer advances in material science and the lessons learned from building the ARC. And it again will be better than the then current, assembled reactors. That is how it is supposed to be.