Do we get to choose?

If this has been answered already I apologize but do we get to choose who play in the campaign? I’m just going by the adds and I’m hoping we do since I’ll pick the MC every time.

In co-op, you can choose who you play as (providing someone hasn’t beaten you to it) but the host is always Locke/Chief

You will be switching back and forth between Locke and Chief during the campaign if i understand it right, so no you will not have a choice of one or the other.