From a geostationary satellite you have 99.5% uptime over the course of a year, with most days having 24 hours of full power. Unlike ground solar you don't need batteries, long-distance wires, excess capacity, or demand management. Over 24 hours, a panel in orbit collects five times as much energy as it would on the ground.

Surely sunlight is less filtered above the atmosphere than below/in it? Also, maybe microwaves pass through the atmosphere with less absorption?

The current plan for solar power stations entail using mirrors to focus it to one spot anyway, so the evolution of that might be space mirrors that convert it to a single frequency before beaming it down to a focal point.

Also, the panels/mirrors can be sun-synchronous to receive sun all the time, reducing the amount of them needed (surface panels would not get peak sunlight all the time, and half the time will be shadowed by earth).

Less affected by cloud albedo and thus more effectively contributing to global warming by increasing the amount of energy that makes it through the atmosphere. That's tongue-in-cheek of course, but I do find it interesting that not many seem concerned about this problem. The experiments have almost no effect of course but if this were ever done on a large scale...

There are a few more "advantages" (if one wants to frame it that way) over collecting sunlight on the surface, for one the sun always shines in space and depending on the satellite's orbit it could collect energy almost 24/7. It could also be sent to different ground stations depending on demand. In theory, if it ever became viable.

You can beam it to remote areas where there is little sunlight (or it is night-time) and where they may not have access to cheaper energy supplies.

Long enough waves go around raindrops and thus right through clouds.

You can transmit on specific wavelengths which means weather would be less of an issue and this could transmit at night.