Of course panel design is solely up to the designer but in general there is some standards that you will see as you come across different applications.
With the tightening of NFPA 70E electrical code We at our location have started specifying all cabinets have the higher voltages separated from the lower voltages so that it lowers the arc flash rating on the low voltage cabinet and thus use of arc flash protection isn’t required. This allows us to open the plc/ controls cabinets without using arc flash protection, but arc flash protection has to be used when opening the 480 drives cabinets.
Also there is the need to keep controls cabling away from high voltage and high frequency noise. By separating the cabinets this helps keep your ethernet and controls signal cables away from noise causing conductors.
Ultimately the decision has to do with your space and machine requirements. If space (and cost) isn’t a concern 2 cabinets are the best. But if you are building a small machine in which all controls could fit in a single smaller cabinet (3’x 4′ or less) then 2 separate cabinets become a little much.
Just my opinion.