There are several reasons to go with the SCD30 over the MH-Z series. Depending on the use none of them may be critically important, but here they are:
SCD30:
uses 1/2 the power
has better accuracy
has a longer operational lifespan
has 5X higher detection range
has onboard humidity compensation
has I2C bus in addition to UART
has accurate and detailed English documentation
I2C bus and up to 10K ppm are the big ones, for home or industrial use these are important, for standalone office ‘too many people not enough airflow’ sensing, probably not