2017-2018 models have PCM 4.0 which is a big improvement over 3.1.
However, coming from the X4MC the S is going to feel really slow. Adding a tune can help, but both the S and GTS have the smaller 3.0 engine vs the 3.6 on the Turbo, so your gains are going to be limited.
If you are set on getting out of the X4MC I would keep looking around for better options. Unfortunately prices on everything are sort of stupid right now.
