There is the possibility that they can combine both strategies:
Have a massive protest in Tehran to tie down a percentage the military / security forces and ensure some external news coverage from foreign reporters based in Tehran while other protests in other Iranian cities have more of a free hand to operate because of the concetration of security in Tehran. This gets their message out to the world, to more of the people beyond those in Tehran and keeps the mullahs playing the shell game regarding military and security resources. As the outer city protests get more word of mouth, they can stream more people into Tehran or bud off more protests into smaller and smaller cities / towns.
Eventually the mullahs will face a shortage of those loyal to them compared to the number of people in the streets protesting the Iranian government.