Simple!, in one brutal sentence :)

- EVEE: No photorealism. It's like a sophisticated "game engine" renderer but no photorealistic.
But actually nothing comparable for example to the beast: UNITY! (and also UNREAL)

- CYCLES: if you NEED photorealistic renderings.
Very high rendering times obviously, even if you have a super powerful machine.
But it's one of the BEST renderer of the market.