sonofjones said:
Darth Maul could've been the Darth Vader of the PT had he not been killed off so early)
Darth Vader was a developed character with an arc.
Darth Maul was a throwaway villain with no personality and as you say, he dies before anything compelling could come of him.
So it's a pretty useless comparison to draw if it hinges on a hypothetical "If they'd done it differently" scenario. Just saying.