Once one is granted, the other application will be terminated, as you are no longer eligible to apply. In other words, a PR cannot apply to be a PR, so once you've become a PR, the second PR application will be closed.
Note that the fees won't be refunded if they've started processing an application, however.
But if someone has the choice of CEC versus inland spousal, I routinely recommend CEC - you get your letter from CPC-S in 2 months and with that you can extend your work permit (a "bridging open work permit"). Usually, you're done with CEC in 13 months, so by the time spousal get's AIP (and thus the work permit) a CEC applicant has become a permanent resident.
Plus, CEC isn't conditional (but spousal is if you haven't been married two years or have children at the time of application) and the sponsor hasn't promised to take care of the applicant for three years...