Elm is heavily focused on user-friendliness and offers a sort of full framework for developing frontend applications, whereas PureScript is focused on producing

Elm is heavily focused on user-friendliness and offers a sort of full framework for developing frontend applications, whereas PureScript is focused on producing readable, easily interopable javascript (and javascript only). That is by no means a comprehensive comparison, but those are the main differentiating factors I can see as someone who has been watching both projects for a long time.