Engineers who are capable of both give you far more flexibility. This is more important on a small team than a large engineering department. Note that they don'

Engineers who are capable of both give you far more flexibility. This is more important on a small team than a large engineering department. Note that they don't have to be equally strong in both, just capable of contributing good code if you have an imbalance of work on one side or the other for a few sprints or if the person who's stronger on the other end is on vacation or busy firefighting or whatever.