[sam]

ITER and Commonwealth can (and in my opinion should) be seen as complimentary endeavors.

ITER has been designed with relatively conservative magnet technology and will very likely provide the physics results that need to be understood in order for fusion power to become a reality. This includes experimental tests of the physics of plasmas where the heating is dominated by high energy alpha particles rather than external heating. This is a regime that's not yet been studied in a laboratory and there is important research to be done there.

Commonwealth is pushing the envelope of high temperature superconductor magnet technology and is relatively high risk compared to ITER's magnets (and this is a good thing). Lots of ITER technology will be useful to Commonwealth even before ITER turns on. For example decisions about which low activation steels and the huge amount of physics work that's already gone into planning for ITER.

I think the most likely outcome is that both accomplish their goals and contribute to making commercially viable fusion energy a reality in the future.