In reality the MCU I/O pin drive current capability will likely be the greatest limit to switching speeds. A relatively low value resistor, a few hundred ohms, is advised to limit the peak current at turn on/off to a safe value as specified for the MCU. You could do without, but good design practice says you should limit the current. Resistors are also valuable to help swamp gate drive instability, which is unlikely with an MCU output, due to the low current capability.
paul