A selection of other electric vertical-takeoff and landing aircraft :

Comparison by lift/power

– estimated from disk-loading (pressure difference across rotor)

The RingWing (green) is the most efficient at the assumed 330Kg weight.

The lilium is clearly inefficient in hover, but their strategy (see lilium blog) assumes limited time period spent in the power-hungry hover mode” and instead optimises for “efficient cruise flight” and “low noise”.

However negotiating obstacles, to meet objective 1, requires significant time in hover and low-speed flight, and high power would require expensive batteries and non-standard electrical components that are incompatible with the objective of an affordable vehicle.

Comparison of RingWing (green) with conventional VTOL aircraft