Engine technology is driven by pure innovation and the desire to develop new skills whilst pushing everything to the next level, continuously. Unreal like other raster engines provides a gateway to this world, whereas Lumion and its analogues do not. Any architect who realises this will probably benefit from Unreal, whilst the rest will probably prefer Lumion as a means to an end…
Unreal is an order of magnitude more powerful, and it is free. The catch … it requires some effort, and a change in perception.
Cheers