Compared with coaxial cable, microstripline:

Coaxial cable features a center conductor completely surrounded by an outer metallic shield, which provides excellent isolation from external electromagnetic interference and prevents the signal from radiating outward. In contrast, a microstripline consists of a conducting trace on the top layer of a printed circuit board with a ground plane underneath. Because the top of the conducting trace is exposed to the air and not enclosed by a shield, it is much more susceptible to picking up stray signals and radiating its own RF energy. Therefore, the primary disadvantage of microstripline compared to coaxial cable is its significantly poorer shielding. Impedance is not the deciding factor here, as both microstripline and coaxial cable can be designed to match standard characteristic impedances like 50 ohms.