Two grounds when using transistor switching
If you have analog signals crossing the boundary, and that is your "analog ground" in the sense that it is the reference for all of your analog signals, then I think the high side switch is less likely to give you problems. The low side switch will introduce a potentially nasty voltage between the two references due to its finite on-resistance and need to handle the switching current from the digital logic. The "digital" ground could also be the reference for internal ADCs, for example.

As others have commented, a P-channel MOSFET is a better choice for a high side switch. It is a good idea to decouple the MCU side to provide a low impedance source for the switching current.