Why is it recommended to couple a big solar panel with a small microinverter?

Installing solar modules with wattages higher than microinverter maximum output, leads to more efficient and dependable systems. The reason for this is that in most hours of the day, the sun conditions are such that the solar panel does not produce its maximal Wattage. The losses in the hours of peak production may not justify the additional cost of a larger microinverter.

A more detailed explanation of a research done on this topic is outlined in this blog post:
Bigger Is Better: Big Solar Modules For Small Microinverters