[lxgr]

The first downside of LEO applies only to COSPAS-SARSAT, but not e.g. Iridium.

Iridium has inter-satellite links and the satellites accordingly don‘t need to store a message until they are in view of a ground station again – message delivery is effectively instant, globally.

Unlike PLBs, Iridium devices require a paid subscription, though.

[almog]

It is my understanding that inter-satellite links makes communication effectively instant, not ground to satellite delivery in challenging environment, such as deep canyons (especially north to south ones) with narrow view of the sky. GEO might fail under these conditions too, but when it suceeds, delivery is immediate.

Moreover, GPS can be flaky under such conditions too, in which case MEO satellites might be able to provide fast Doppler detection to approximate the device location to few miles area and responders can further reduce the search area.

On the other hand, satellite tracker (such as Garmin InReach) advantage would be that it can be configured to try and send its location every 10 minutes, therefore, even if at the current location there's no signal, your last tracked location might be not far away.