I used both concurrently for over five years, and Patrick covered the main points. I preferred the gamut mapping of the Monaco profiles especially in blues and reds. Monaco is much less flexible in the targets and formats that it will take. Browsing to a folder containing a spectral file crashes Monaco on my machine.
Profilemaker has some benefits with respect to spectral data, with some sort of optical brightener compensation and tuning to a specific light source. You can also make a profile from just about any profiling chart.
Overall, I would recommend Monaco. I am hoping for a new program that combines the best of both programs, but I am not holding my breath.
Bret