The verdict
If you have to pick one, and you are on Google Workspace or deal with many outsiders, I'd pick Google Calendar. Nearly everyone can open a Google invitation, and a team needs one shared view of who is free. If your calendar is already fine and you lose hours to social feeds and news sites, I'd pick Freedom. A calendar block labelled deep work does nothing when your phone is in your hand. Freedom is the part that enforces it. For most founders the sensible answer is both, with the calendar deciding when to focus and Freedom making sure you do.