i'd trust mitsubishi more than the pioneer/mrcool. Mitsubishi has been in the mini-split game a long time. They have many local dealers/installers. The one you linked to also has a higher seer. Are you going to diy? Do you have the tools to install (vacuum pump, gauges, soldering equipment, etc?
You need to size the a/c unit correctly, google an a/c (btu) calculator. To large a unit and it will be constantly short cycling and leave you with an overly humid environment.