Addressed in the FAQ:

How is Blip different to nearby sharing like AirDrop? Apple’s “AirDrop” and Google’s “Nearby Share” can be really handy. However, they aren’t compatible with each other and require devices to be physically next to each other. They are also unreliable when transferring large files, and will often lose your progress.

Blip doesn’t need devices to be nearby, so it’s much more reliable. Blip works wherever your internet connected devices are in the world, and works regardless of what kind of device you own. You can transfer from Android to Mac, Windows to iPhone, iPad to Android—you name it!