Fokker would have chosen the best engine available at the time and one which the customer would accept and support.
The SAAB 340 design was initially planned to offer GE or PW engines. Very soon after the launch customer sentiment was very in favour of the GE product so the PW option was dropped.
Sometimes you can offer the next gen engine and customers don't like it and go with older tech because they know its reliability and cost factors. If the S2000 had launched on time and got the two year lead on the 50 seat RJs things may have been different.