While the argument looks logical, its perhaps incorrect.
Market Cap is not derived from EV. It is the other way round.Market Cap is determined by the price investors are willing to pay for a share in the business, which changes dynamically in the market. EV is a derived Value.
My point is for any ratio to be meaningful, the numerator and denominators have to be consistent. You cant ROIC on top (which is debt agnostic) and take EV in the bottom (which uses debt).
This aspect is emphasised in the Copeland Valuation Book, pgs 163-164, when it points out the inconsistencies of using say Return on Total Assets. Have a look.
In any case, we should first see what the data throws out, and no harm in computing both sets of figures for comparisons sake across companies - I guess we will know better.
-Donald