You need to hold one fee-based Ultimate Rewards card to maximize the value of the points. Downgrading from INK Plus (or Bold) to INK Cash (or Classic) was a straightforward decision because the bonus categories of the free cards overlapped with the paid cards. However, changing from Preferred to Cash will involve trade-offs which will vary by individual.
I currently hold a CSR. What trade offs are you referring to? I have the travel overlap on both cards so I'd be looking at the ink cash to maximize the 5x (note, I'm not referring to manufacturing spend).